diff --git a/README.md b/README.md
index 3e2918a..3dd679e 100644
--- a/README.md
+++ b/README.md
@@ -33,11 +33,13 @@ For server
 - DEFAULT_RESPONSE_REQUEST(p-server only): 3(-1 is INF)
 - USE_TRACE
 - USE_NO_QUEUE
+- SLOW_SERVER(microsecond unit): if turn on sendfile option, DEFAULT_SEND_FILE_CHUNK_SIZE/SLOW bytes/usec, otherwise (buf_size/SLOW_CLIENT) bytes/usec
 
 For client
 - MUL_CLIENT(second unit)
 - SLOW_CLIENT(microsecond unit, (buf_size/SLOW_CLIENT) bytes/usec)
-- DEFAULT_PROGRESS_BAR_WIDTH: 30
    
 For both
-- TIMEOUT: 5(second unit)
\ No newline at end of file
+- TIMEOUT: 5(second unit)
+- MAX_TERMINAL_ROW
+- DEFAULT_PROGRESS_BAR_WIDTH: 30
\ No newline at end of file
diff --git a/server.c b/server.c
index 2f89ec8..6411a39 100644
--- a/server.c
+++ b/server.c
@@ -61,8 +61,10 @@ enum{
  MAX_THREAD_NUMBER = DEFAULT_MAX_THREAD_NUMBER
 #endif
 };
-#define USE_TRACE
-
+#ifdef SLOW_SERVER
+//micro second unit
+static const int SLOW_SERVER_TIME = SLOW_SERVER;
+#endif
 
 /*========
  *Operation
@@ -186,6 +188,9 @@ int send_response(int sock,int fd, uint8_t * buf, size_t bufsize){
             return -1;
         }
         DisplayProgressBar(&pbar,offset,r.file_size,"",false);
+        #ifdef SLOW_SERVER
+            usleep(SLOW_SERVER_TIME);
+        #endif
     }
 #else
     while (offset < r.file_size)
@@ -200,8 +205,10 @@ int send_response(int sock,int fd, uint8_t * buf, size_t bufsize){
             return -1;
         }
         offset += readed;
-        usleep(500000);
         DisplayProgressBar(&pbar,offset,r.file_size,"",false);
+    #ifdef SLOW_SERVER
+        usleep(SLOW_SERVER_TIME);
+    #endif
     }
     DisplayProgressBar(&pbar,offset,r.file_size,"",true);
 #endif