Kad network has become a main kind of file-sharing Peer-to-Peer(P2P) network
leading to the increasing demand of censoring it.In order to accurately determine the censoring object
the problem of optimal peer identification will be put forward.This paper tries to solve this problem.Kad network peer information crawler is designed and implemented to crawl peer information of multiple candidate identifications relationship in real Kad network.Experimental results show that {userID} is the optimal peer identification.