The invention relates to a hydraulic membrane reciprocating pump and provides a positioning pressure releasing system of the hydraulic membrane reciprocating pump and based on deflection deformation of a membrane sheet. The system comprises a release groove communicating with a hydraulic oil channel; a valve rod with an internal cavity is arranged in the hydraulic oil channel; a push-pull rod is arranged in the valve rod in a penetrating mode; a blocking piece is arranged at one end of the push-pull rod, and the other end of the push-pull rod is fixedly connected with the membrane sheet; the push-pull rod can conduct reciprocating movement relative to the valve rod under driving of the membrane sheet; a pressure releasing hole is formed in the side wall of the valve rod; when the membrane sheet normally operates, the pressure releasing hole and the release groove keep misplacement and do not communicate with each other; and when the deflection deformation stroke of the membrane sheet is larger than the maximum length of the internal cavity of the valve rod, the blocking piece drives the valve rod to move relative to a cylinder body, and the pressure releasing hole and the release groove are in the communicating state. According to the positioning pressure releasing system, the situation that the membrane sheet does not generate excessive deformation can be guaranteed, the service life is effectively prolonged, product performance is reliable, the failure rate is very low, misoperation is eliminated, and the normal operation period of the membrane pump is greatly prolonged.