Differential pressure control valve with non-return function

Disclosed is a pressure-gradient control valve with check function, provided with a main valve (2). The main valve body is provided with a valve seat (23) and an on-off member (22) inside, and the on-off member is in transmission connection with a piston (17) controlling on-off of the on-off member piston and the valve seat. The pressure-gradient control valve is characterized in that: through a control pipe line (6), one of entrances of main valve body (1) is connected with a lower control room (10) of a pressure-gradient guide valve (11), and through a one-way valve (7), the other one of the entrances of main valve body (1) is connected with a pressure adjustment cavity (14) of the pressure-gradient guide valve and an upper cavity (16) of main valve piston; through the control pipe line, one of exits of main valve body (21) is connected with an upper control room (13) of the pressure-gradient guide valve and the pressure adjustment cavity (14), and through a one-way valve (15), the other one of the exits of main valve body (21) is connected with the upper cavity (16) of main valve piston. Being capable of automatically adjusting the entrances and the exits of the valve body to keep the pressure-gradient at the preset value, provided with the check function, the utility model is suitable for the ductwork that centralized water-supply is required to be evenly pressured to be allocated to each water-use unit, and can be widely used in places with heating and ventilation, air-conditioning and drainage.