On the basis of g-C3N4nanosheets prepared by liquid phase ultrasonic exfoliation, Ag/g-C3N4nanosheets were fabricated by loading Ag nanoparticles through the method of light reduction. The as-prepared samples were characterized by TEM, FT-IR, XRD, BET and transient photocurrent. The disinfection of Escherichia coli(E. coli) was studied to evaluate the photocatalytic activity under visible light. The photocatalytic antibacterial kinetics were researched by modified Hom model. The results show that 3% Ag/g-C3N4 nanosheets exhibit the optimal photocatalytic disinfection of E. coli and the k2 value of 3% Ag/g-C3N4 nanosheets is 2.99 times of bulk g-C3N4 and 1.45 times of 3% Ag/bulk g-C3N4. Large specific surface area and high photocarrier separation efficiency have resulted in the excellent photocatalytic antibacterial activity of 3% Ag/g-C3N4 nanosheets.