Q: i lost iPhone ,what i have to do?

Where did u lose it?

according to your products, it says you have ios 4.3.1. If you were upgraded, you would be able to use find my iphone to track, lock, and even erase your phone. Unless you are running a later software, I can't help you

well it seems my reply will be a bit late at this point in time, but for future references, go to https://www.icloud.com/#find and see if you can locate it