Platelet has the basic function of hemostasis and maintaining vascular integrity, recent studies have proved that it plays an important role in immune defense against bacterial infection. When bacterial infection occurs, platelet firstly migrate to the infection frontline to identify, bind, endocytose pathogens or release a variety of platelet microbicidal protein, which can directly kill bacteria, strengthen the innate immune function of neutrophil, monocyte and complement system, promote T lymphocyte and B lymphocyte to initiate adaptive immune responses against bacteria.