Protocol reverse engineering is widely used in intrusion detection system, deep packet inspection, fuzzy testing, C & C malware detection, and other fields. First, the formal definition and basic principle of protocol reverse engineering are given. Then, the existing protocol reverse methods based on network trace are analyzed in detail from two aspects of protocol format extraction and protocol state machine inference. In addition, the basic modules, main principles, and characteristics of these algorithms are explained. Finally, the existing algorithms are compared from several aspects, and the development trend of protocol reverse technology is discussed.