The invention discloses a manual valve antifouling mechanism, and belongs to the field of valve equipment. The manual valve antifouling mechanism includes a valve antifouling protection ring, the outer end of the valve antifouling protection ring is fixedly connected to a nodular cast iron protection pipe, the middle of the nodular cast iron protection pipe is rotatably connected to a self-cleaning valve body operation center shaft, and a self-cleaning valve body is arranged on the lower side of the self-cleaning valve body operation center shaft; and the self-cleaning valve body is fixedly connected with the lower end of the nodular cast iron protection pipe, the left and right ends of the self-cleaning valve body are fixedly connected to double-clip type connecting flanges correspondingly, and the valve antifouling protection ring is located in the middle position of the nodular cast iron protection pipe. According to the manual valve antifouling mechanism, proceeding of biological corrosion is limited while pollution and damage of marine microorganisms are hindered through a built-in structure, then a manual valve with aging cracks is protected, and compared with manual valves breeding the marine microorganisms, the service life of the manual valve is greatly prolonged.