Abstract: Social network is a complex network with interaction characteristics. It can link nodes in different social networks by using the network characteristics of complex network, analyze the connections between nodes, and combine with the related matching algorithm to identify user’s virtual accounts, which can help social networks to provide users with better services. This paper presents a systematic review on across social networks user identification techniques proposed in the field of data mining. Then the methods for calculating the similarity of the three types of user identification techniques and the unified identification framework are elaborated in detail. The relevant evaluation metrics are used to evaluate the classified user identification technique performances. Finally, the future research directions of across social networks user identification techniques are prospected based on the analysis of the research status.