The invention belongs to the field of a medical apparatus, and relates to an automatic stripping mechanism for a medical water knife. The automatic stripping mechanism comprises a screw nut mechanism and a clutch device. The automatic stripping mechanism is characterized in that a motor drives the nut to rotate through a synchronous belt; rotation of the nut is changed into linear movement of the screw through the screw nut mechanism; the front end of the screw drives a stripping push block and struts U-shaped elastic retainer rings of two clutch parts which are symmetrical at the left and right at the same time, so as to achieve separation of two groups of plunger pistons and clutch blocks; meanwhile, the stripping push rod contacts wedge blocks on upper and lower cassettes of the medical pump via a line; the tail end of the screw drives the stripping push rod to move in a straight line, so that the upper and lower cassettes of the medical pump are opened; and the medical pump and a cylinder body holder are separated, so as to finish automatic stripping of the medical pump.