Complement is a non-heat-resistant component present in fresh serum that helps specific antibodies to mediate lysis. It is a necessary complement for antibodies to exert their lytic effect and is therefore called complement. It includes more than 30 soluble and membrane-bound proteins that make up the complement system. The biological significance of complement: 1, participate in early host immunity against infection 2, maintain the stability of the body’s internal environment, 3, participate in adaptive immunity, 4, the complement system and coagulation, fibrinolysis, kinin system is closely related to each other and regulate each other.