The pressure-reducing valve is designed to reduce the inlet pressure to a desired outlet pressure and rely on the energy of the medium itself to keep the outlet pressure automatically stable. From fluid mechanics point of view, pressure reducing valve is a throttling element, local resistance to change that by changing the throttling area, change the kinetic energy of the flow velocity and fluid, different pressure loss, so as to achieve the goal of decompression. Then, the control and adjustment system is used to balance the pressure fluctuation of the valve and the spring force, so that the pressure of the valve remains constant within a certain error range.