How to tracking time for each instruction when use debug mode(KEIL C51)? I have used Franklin (PV32) and it can display in uS.
Depends on what "debug mode" you're talking of. The simulator integrated in C51 will just show you the time (and a CPU cycle count, too) in the "register" pane while debugging. For more automated analysis, there's the performance analyzer which lets you time entire functions, but also smaller code fragments.