diff --git a/backend/api/handlers.go b/backend/api/handlers.go
index fbd99ad..563a4b9 100644
--- a/backend/api/handlers.go
+++ b/backend/api/handlers.go
@@ -1,6 +1,7 @@
 package api
 
 import (
+	"ai-gateway/internal/billing"
 	"ai-gateway/internal/db"
 	"ai-gateway/internal/logger"
 	"ai-gateway/internal/models"
@@ -16,7 +17,6 @@ import (
 	"time"
 
 	"github.com/gin-gonic/gin"
-	"github.com/pkoukk/tiktoken-go"
 	"gorm.io/gorm"
 )
 
@@ -146,7 +146,8 @@ func (h *APIHandler) ChatCompletions(c *gin.Context) {
 	}
 
 	// 使用tiktoken精确计算请求token数
-	requestTokenCount := calculateTokenCount(req.Messages)
+	messages := convertToTikTokenMessages(req.Messages)
+	requestTokenCount := billing.CalculateMessagesTokensSimple(messages)
 
 	// 选择后端模型
 	backendModel, err := router.SelectBackendModel(h.DB, req.Model, requestTokenCount)
@@ -273,7 +274,7 @@ func (h *APIHandler) ChatCompletions(c *gin.Context) {
 			if choice, ok := choices[0].(map[string]interface{}); ok {
 				if message, ok := choice["message"].(map[string]interface{}); ok {
 					if content, ok := message["content"].(string); ok {
-						responseTokenCount = calculateTokenCountFromText(content)
+						responseTokenCount = billing.CalculateTextTokensSimple(content)
 					}
 				}
 			}
@@ -281,13 +282,8 @@ func (h *APIHandler) ChatCompletions(c *gin.Context) {
 	}
 
 	// 计算费用
-	var cost float64
-	switch backendModel.BillingMethod {
-	case models.BillingMethodToken:
-		cost = float64(requestTokenCount)*backendModel.PromptTokenPrice + float64(responseTokenCount)*backendModel.CompletionTokenPrice
-	case models.BillingMethodRequest:
-		cost = backendModel.FixedPrice
-	}
+	costCalculator := billing.NewCostCalculator()
+	cost := costCalculator.CalculateModelCost(backendModel, requestTokenCount, responseTokenCount)
 
 	// 创建日志记录
 	logEntry := &models.RequestLog{
@@ -325,7 +321,7 @@ func (h *APIHandler) ResponsesCompletions(c *gin.Context) {
 
 	var req ResponsesRequest
 
-	// 解析请求\u4f53
+	// 解析请求体
 	if err := c.ShouldBindJSON(&req); err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{
 			"error": gin.H{
@@ -337,7 +333,8 @@ func (h *APIHandler) ResponsesCompletions(c *gin.Context) {
 	}
 
 	// 使用tiktoken精确计算请求token数
-	requestTokenCount := calculateTokenCount(req.Messages)
+	messages := convertToTikTokenMessages(req.Messages)
+	requestTokenCount := billing.CalculateMessagesTokensSimple(messages)
 
 	// 选择后端模型
 	backendModel, err := router.SelectBackendModel(h.DB, req.Model, requestTokenCount)
@@ -426,7 +423,7 @@ func (h *APIHandler) ResponsesCompletions(c *gin.Context) {
 			if choice, ok := choices[0].(map[string]interface{}); ok {
 				if message, ok := choice["message"].(map[string]interface{}); ok {
 					if content, ok := message["content"].(string); ok {
-						responseTokenCount = calculateTokenCountFromText(content)
+						responseTokenCount = billing.CalculateTextTokensSimple(content)
 					}
 				}
 			}
@@ -434,13 +431,8 @@ func (h *APIHandler) ResponsesCompletions(c *gin.Context) {
 	}
 
 	// 计算费用
-	var cost float64
-	switch backendModel.BillingMethod {
-	case models.BillingMethodToken:
-		cost = float64(requestTokenCount)*backendModel.PromptTokenPrice + float64(responseTokenCount)*backendModel.CompletionTokenPrice
-	case models.BillingMethodRequest:
-		cost = backendModel.FixedPrice
-	}
+	costCalculator := billing.NewCostCalculator()
+	cost := costCalculator.CalculateModelCost(backendModel, requestTokenCount, responseTokenCount)
 
 	// 从上下文获取API密钥
 	apiKeyValue, exists := c.Get("apiKey")
@@ -480,38 +472,16 @@ func (h *APIHandler) ResponsesCompletions(c *gin.Context) {
 	c.Writer.Write(responseBody)
 }
 
-// calculateTokenCount 计算消息列表的token总数
-func calculateTokenCount(messages []ChatCompletionMessage) int {
-	encoding, err := tiktoken.GetEncoding("cl100k_base")
-	if err != nil {
-		log.Printf("Failed to get tiktoken encoding: %v", err)
-		return 0
+// convertToTikTokenMessages 将ChatCompletionMessage转换为billing包的消息格式
+func convertToTikTokenMessages(messages []ChatCompletionMessage) []billing.ChatCompletionMessage {
+	result := make([]billing.ChatCompletionMessage, len(messages))
+	for i, msg := range messages {
+		result[i] = billing.ChatCompletionMessage{
+			Role:    msg.Role,
+			Content: msg.Content,
+		}
 	}
-
-	totalTokens := 0
-	for _, msg := range messages {
-		// 每条消息的基础开销（role + 分隔符等）
-		totalTokens += 4
-		// role的token数
-		totalTokens += len(encoding.Encode(msg.Role, nil, nil))
-		// content的token数
-		totalTokens += len(encoding.Encode(msg.Content, nil, nil))
-	}
-	// 对话的基础开销
-	totalTokens += 2
-
-	return totalTokens
-}
-
-// calculateTokenCountFromText 从文本计算token数
-func calculateTokenCountFromText(text string) int {
-	encoding, err := tiktoken.GetEncoding("cl100k_base")
-	if err != nil {
-		log.Printf("Failed to get tiktoken encoding: %v", err)
-		return 0
-	}
-
-	return len(encoding.Encode(text, nil, nil))
+	return result
 }
 
 // handleStreamingResponse 处理流式响应
@@ -607,16 +577,11 @@ func handleStreamingResponse(c *gin.Context, resp *http.Response, requestTimesta
 	}
 
 	// 计算响应 token 数
-	responseTokenCount := calculateTokenCountFromText(fullContent.String())
+	responseTokenCount := billing.CalculateTextTokensSimple(fullContent.String())
 
 	// 计算费用
-	var cost float64
-	switch backendModel.BillingMethod {
-	case models.BillingMethodToken:
-		cost = float64(requestTokenCount)*backendModel.PromptTokenPrice + float64(responseTokenCount)*backendModel.CompletionTokenPrice
-	case models.BillingMethodRequest:
-		cost = backendModel.FixedPrice
-	}
+	costCalculator := billing.NewCostCalculator()
+	cost := costCalculator.CalculateModelCost(backendModel, requestTokenCount, responseTokenCount)
 
 	// 创建日志记录
 	logEntry := &models.RequestLog{
diff --git a/backend/internal/billing/calculator.go b/backend/internal/billing/calculator.go
new file mode 100644
index 0000000..e6a4988
--- /dev/null
+++ b/backend/internal/billing/calculator.go
@@ -0,0 +1,132 @@
+package billing
+
+import (
+	"ai-gateway/internal/models"
+	"log"
+
+	"github.com/pkoukk/tiktoken-go"
+)
+
+// TokenCalculator 提供token计算功能
+type TokenCalculator struct {
+	encoding *tiktoken.Tiktoken
+}
+
+// NewTokenCalculator 创建一个新的TokenCalculator实例
+func NewTokenCalculator() (*TokenCalculator, error) {
+	encoding, err := tiktoken.GetEncoding("cl100k_base")
+	if err != nil {
+		return nil, err
+	}
+	return &TokenCalculator{encoding: encoding}, nil
+}
+
+// CalculateMessagesTokens 计算消息列表的token总数
+// 根据OpenAI的token计算规则：
+// - 每条消息有4个token的基础开销（role + 分隔符等）
+// - role字段的token数
+// - content字段的token数
+// - 整个对话有2个token的基础开销
+func (tc *TokenCalculator) CalculateMessagesTokens(messages []ChatCompletionMessage) int {
+	totalTokens := 0
+	for _, msg := range messages {
+		// 每条消息的基础开销（role + 分隔符等）
+		totalTokens += 4
+		// role的token数
+		totalTokens += len(tc.encoding.Encode(msg.Role, nil, nil))
+		// content的token数
+		totalTokens += len(tc.encoding.Encode(msg.Content, nil, nil))
+	}
+	// 对话的基础开销
+	totalTokens += 2
+
+	return totalTokens
+}
+
+// CalculateTextTokens 从文本计算token数
+func (tc *TokenCalculator) CalculateTextTokens(text string) int {
+	return len(tc.encoding.Encode(text, nil, nil))
+}
+
+// ChatCompletionMessage 聊天消息结构
+type ChatCompletionMessage struct {
+	Role    string
+	Content string
+}
+
+// CostCalculator 提供费用计算功能
+type CostCalculator struct{}
+
+// NewCostCalculator 创建一个新的CostCalculator实例
+func NewCostCalculator() *CostCalculator {
+	return &CostCalculator{}
+}
+
+// CalculateCost 根据计费方式计算费用
+// 支持两种计费方式：
+// - token: 按token计费，分别计算输入和输出token的费用
+// - request: 按请求次数计费，使用固定价格
+func (cc *CostCalculator) CalculateCost(
+	billingMethod string,
+	requestTokenCount int,
+	responseTokenCount int,
+	promptTokenPrice float64,
+	completionTokenPrice float64,
+	fixedPrice float64,
+) float64 {
+	switch billingMethod {
+	case models.BillingMethodToken:
+		return float64(requestTokenCount)*promptTokenPrice + float64(responseTokenCount)*completionTokenPrice
+	case models.BillingMethodRequest:
+		return fixedPrice
+	default:
+		log.Printf("Unknown billing method: %s, defaulting to 0 cost", billingMethod)
+		return 0
+	}
+}
+
+// CalculateModelCost 根据后端模型配置计算费用
+func (cc *CostCalculator) CalculateModelCost(
+	backendModel *models.BackendModel,
+	requestTokenCount int,
+	responseTokenCount int,
+) float64 {
+	return cc.CalculateCost(
+		backendModel.BillingMethod,
+		requestTokenCount,
+		responseTokenCount,
+		backendModel.PromptTokenPrice,
+		backendModel.CompletionTokenPrice,
+		backendModel.FixedPrice,
+	)
+}
+
+// CalculateMessagesTokensSimple 简化的消息token计算函数（不需要创建calculator实例）
+func CalculateMessagesTokensSimple(messages []ChatCompletionMessage) int {
+	encoding, err := tiktoken.GetEncoding("cl100k_base")
+	if err != nil {
+		log.Printf("Failed to get tiktoken encoding: %v", err)
+		return 0
+	}
+
+	totalTokens := 0
+	for _, msg := range messages {
+		totalTokens += 4
+		totalTokens += len(encoding.Encode(msg.Role, nil, nil))
+		totalTokens += len(encoding.Encode(msg.Content, nil, nil))
+	}
+	totalTokens += 2
+
+	return totalTokens
+}
+
+// CalculateTextTokensSimple 简化的文本token计算函数（不需要创建calculator实例）
+func CalculateTextTokensSimple(text string) int {
+	encoding, err := tiktoken.GetEncoding("cl100k_base")
+	if err != nil {
+		log.Printf("Failed to get tiktoken encoding: %v", err)
+		return 0
+	}
+
+	return len(encoding.Encode(text, nil, nil))
+}