Abstract: Protocol reverse engineering is an important way to analyze private protocols, which can infer the protocol constraints and specifications with little or no prior knowledge, so protocol reverse engineering has practical value in malware supervision, protocol fuzz testing and vulnerability detection, interaction behavior understanding and so on. Network traffic characterizes protocol specifications and bears the inherent characteristics of protocol, so that the private protocol reverse engineering based on network traffic is more suitable for discovering, analyzing and monitoring the private protocol on the network. In this paper, we provide a thorough review of the existing private protocol reverse engineering based on network traffic: Firstly, the architecture of private protocol reverse engineering based on network traffic is proposed, which includes four steps of pre-inference, protocol format inference, semantic analysis, and protocol state machine inference. The main research tasks of each step are also elaborated and a classification structure oriented to the core of the research method is proposed. Secondly, the method and process of each private protocol reverse engineering are described in detail, and a comparative analysis from multiple perspectives of applicable protocol type, technology kernel, and inference algorithms etc is made. A systematic overview of existing private protocol reverse engineering based on network traffic is conducted. Finally, the shortcomings of existing research and main influencing factors are summarized, and the future research direction and application scenarios of private protocol reverse engineering are prospected.