Abstract: Network user identity identification (UII) is significant to maintain network security and promotes the construction of network identity management system. UII is not only the fundamental for user network portrait, action prediction, and accurate delivery service, but also the technical pillar for social bot detection, network social governance, and crack down cybercrime. The progress of UII technology and its applications in bot detection, community detection, and user identity linkage across social networks are analyzed. At first, from the definition and development history of UII, the classification of UII methods is introduced. Second, a brief overview of bot detection methods with different characteristics is performed, and their main applicable scenarios are pointed out. Then, social bots related community detection techniques are analyzed. Furthermore, the existing methods for user identity linkage across social network platforms are surveyed and categorized. Finally, we discusses the current challenges of user identity research and its future prospects.