CurrentPage["PageStartPublish"] like this ,PageStartPublish are from ?
is be defined as pagetype's property,but i can not find in the same template page.
i find this way is widely userd but how to use it?
Not quite sure what you mean, but PageStartPublish is a built in property in EPiServer. Take a look at the SDK, EPiServer Developer's Guide, Properties. You can also search for PageStartPublish and choose the 3'rd item in the result set. There you have all the built in properties in EPiServer.
/Øyvind