With the widespread use of antibiotics，increasing drug-resistant strains bring more challenges to clinical serious infectious disease，therefore，the research and development of the novel antibacterial and agent is in urgency. Phage lysine is a kind of protease which is expressed in the last infectious phase of double-stranded DNA phage and has the ability to crack bacterial cell wall. In re－cent years，studies of phage lysine have showed that it can be cloned and expressed in prokaryocyte，with expressed lysins having po－tency to kill bacteria in vitro and vivo. A number of experiments on animal showed that lysin agents can specifically resist the host bacteria，featuring efficiency，specificity，safety and synergy. These characteristics of phage lysin make it possible to be applied widely in treating clinical drug-resistant diseases.