software of time sync
 

Is any software in Linux which can sync time with my windows 2003 server
through ntp protocol?

I tried ntpd in Linux, it seems not work. my question is:
is there another lan time sync solution ?

ntpd works very well. If you are having a problem with it, there is a configuration problem.

can ntp support sync time in every 20 seconds?

is there any other sofeware which support time sync?

ntpd protocol does not sync every 20 seconds, because that is very inefficient and unnecessary.

ntpd will sync as often as needed to keep your system clock within about 100ms of the clock source. Over time, it creates and maintains a local drift file to locally correct the time, and allow the sync intervals to be extended. Ideally, after a few weeks, it will be many hours or days between syncs.

still not understand.

what is the min time period of time sync? do you mean it is only synced when there is a differ > 100 ms ?

It's not a simplistic protocol. The documentation is here.