Automatic compensating device for sealed clearance of plunger pair

The invention relates to an automatic compensating device for a sealed clearance of a plunger pair, which can be used in a hydraulic pump structure for seawater, fresh water, high water base and other low-viscosity media, and can also be used in an oil hydraulic pump structure. The compensating device comprises a plunger, a gland, a O-ring, an annular groove, a plunger sleeve, a cylinder body, a communication water channel, an accommodating cavity, a hole bottom groove and a choke plug, wherein the plunger sleeve is an elastic element of the engineering plastic and pressed into a cylinder bore in the cylinder body in clearance fit when assembling; the plunger sleeve and the plunger are in clearance fit; the residual space of the plunger sleeve after being embedded with the plunger is the accommodating cavity; an orifice of the cylinder body is provided with the O-ring for preventing high-pressure water from leaking; one end of the orifice of the cylinder body is provided with the gland tightly fixed with the