The valve body is of cast construction. The valve seat adopts the structure of O-ring seal and floating valve seat with pre tightening force to make the inlet and outlet of the valve sealed in both directions; And the opening and closing torque of the structure is only 1/2 of that of ordinary valves, which can easily open and close the valve. The valve seat adopts PTFE inlaid on the sealing surface, which has the double sealing of PTFE to metal and metal to metal. The PTFE sealing surface can simultaneously remove the dirt on the gate. The gate of the valve, whether fully open or fully closed, is always consistent with the sealing surface, and the sealing surface is protected from direct flushing by the medium, thus extending the service life. When the valve is fully opened, the channel is smooth and straight, the flow resistance coefficient is very small, and there is no pressure loss. The pipeline can be cleaned with a hairball. When the valve is closed, the high pressure in the inner chamber can be removed automatically to ensure safe use. The closed gear is used to rotate the opening and closing indicating mechanism, which can clearly reflect the opening and closing of the valve. The external surface of the directly buried valve is treated with epoxy coal tar pitch for corrosion protection, which can last the same life as the pipeline.