diff --git a/apps/iot/src/iot_logger.erl b/apps/iot/src/iot_logger.erl
index 79ff5bd..6415bd0 100644
--- a/apps/iot/src/iot_logger.erl
+++ b/apps/iot/src/iot_logger.erl
@@ -74,7 +74,8 @@ handle_call(_Request, _From, State = #state{}) ->
     {noreply, NewState :: #state{}, timeout() | hibernate} |
     {stop, Reason :: term(), NewState :: #state{}}).
 handle_cast({write, Data}, State = #state{file_path = OldFilePath, file = OldFile}) ->
-    Line = format(Data),
+    Line = <<(time_prefix())/binary, " ", (format(Data))/binary, $\n>>,
+
     FilePath = make_file(),
     case FilePath =:= OldFilePath of
         true ->
@@ -83,7 +84,8 @@ handle_cast({write, Data}, State = #state{file_path = OldFilePath, file = OldFil
         false ->
             file:close(OldFile),
             {ok, File} = file:open(FilePath, [append, binary]),
-            {noreply, State#state{file = File}}
+            ok = file:write(File, Line),
+            {noreply, State#state{file_path = FilePath, file = File}}
     end.
 
 %% @private
@@ -118,13 +120,9 @@ code_change(_OldVsn, State = #state{}, _Extra) ->
 %%%===================================================================
 
 format(Data) when is_binary(Data) ->
-    TimePrefix = time_prefix(),
-    NData = iolist_to_binary(Data),
-    <<TimePrefix/binary, " ", NData/binary, $\n>>;
+    iolist_to_binary(Data);
 format(Items) when is_list(Items) ->
-    TimePrefix = time_prefix(),
-    Line = iolist_to_binary(lists:join(<<"\t">>, Items)),
-    <<TimePrefix/binary, " ", Line/binary, $\n>>.
+    iolist_to_binary(lists:join(<<"\t">>, Items)).
 
 time_prefix() ->
     {{Y, M, D}, {H, I, S}} = calendar:local_time(),
@@ -133,9 +131,9 @@ time_prefix() ->
 -spec make_file() -> string().
 make_file() ->
     {Year, Month, Day} = erlang:date(),
-    Prefix = io_lib:format("~b~2..0b~2..0b-", [Year, Month, Day]),
+    Suffix = io_lib:format("~b~2..0b~2..0b-", [Year, Month, Day]),
     RootDir = code:root_dir() ++ "/log/",
-    lists:flatten(RootDir ++ Prefix ++ ?LOG_FILE).
+    lists:flatten(RootDir ++ ?LOG_FILE ++ "." ++ Suffix).
 
 ensure_dir() ->
     RootDir = code:root_dir() ++ "/log/",