Metering differential pressure valve capable of keeping constant flow when inlet pressure changes

The invention belongs to the technical field of hydraulic machinery, and discloses a device for keeping constant flow during inlet pressure change and a control method. The device comprises a blanking cap, a stop block, a valve, a bushing, a spring and a spring seat, the stop block is connected to the shell through threads and used for fixing the lining and limiting the position of the valve, and the blanking cap is connected to the stop block through threads. The spring is arranged on the right side of the valve; and the spring seat is arranged on the right side of the spring. Compared with an existing metering-pressure difference-oil return mode for controlling constant flow, the structure is simple, and only one set of valve assembly and part of oil nozzles are arranged. According to the structure, an electronic controller, an electro-hydraulic servo valve and a displacement sensor are not needed in control, and the purpose of constant flow is achieved through matching of the throttling valve, the spring a