The invention discloses a method for weight-increasing and antimicrobial treatment of silk fiber, comprising: the preparing of silk fiber, degumming, washing, weight increasing treatment, soaping, dyeing, antibacterial treatment and after-finishing, wherein the weight-increasing treatment is performed at high temperature and pressure, the high temperature is 85 to 90 DEG C, in the weight increasing treatment, a grafting solution is firstly prepared and contains methacrylate ester derivatives as grafting monomer, a initiator, a non-ion or anionic surfactant and degumming waste water. In the invention, the drained degumming waste water can be recycled, thus saving the resource, reducing the pollution, improving the efficiency, and according with the requirement of circular, economical and clean production. In the invention, the weight increasing treatment for the silk fiber is performed, at the same time, the antimicrobial treatment is also completed, thus the treated silk fiber has the ideal weight-increasing effect and a certain of antimicrobial performance.