The invention relates to an overpressure stop valve which is composed of a valve body, two sets of cylinder sleeves, pistons, return springs, stop pins, fluid directors and connectors. The valve body is of a tubular structure, one cylinder sleeve is arranged at one end of an inner hole of the valve body, one piston is arranged in the cylinder sleeve, one return spring is arranged between a piston shaft and the cylinder sleeve, one stop pin is arranged on the piston shaft, the outer end of the cylinder sleeve is connected with one connector, and one fluid director is arranged between the cylinder sleeve and the connector. The other end of the inner hole of the valve body is arranged symmetrical with the structure and is sequentially provided with one cylinder sleeve, one piston, one return spring, one stop pin, one connector and other parts. In an initial state, it needs to be guaranteed that the interiors of the two connectors are kept in an intercommunicated state through the structures and the positions of the parts. The overpressure stop valve has the advantages that the overpressure stop valve is installed on a gas pipeline, when flow or pressure of a user side on the pipeline differs to a certain degree, a gas source can be emergently cut off, and therefore normal operation of a pipe network and use safety of a user are guaranteed.