The invention discloses a hard top plate waterflooding pressure relief treatment method. The method comprises the following steps of S1, according to a stratum histogram, through combination with a rock mechanical property test, carrying out preliminary analysis on positions and development case of top plate separation fractures, S2, when cutting depth at an open-off cut on the work surface is in a range of 13-17m, drilling a row of holes on the top plate at a certain angle along a work surface advance direction, and observing top plate rock stratum crack development case by a borehole camera, S3, further detecting top board crack development case by a double-head water-plugging device detection system, S4, determining a top plate rock stratum crack development range and depth according to the results of the above three steps, and pouring high pressure water into the cracks by a high pressure water pump so that hard top plate integrity is broken and rock strength is reduced, and S5, after top plate pressure is released, sequentially pushing the work surface and repeating the above processes until work surface exploitation is finished. The method can realize accurate positioning of a pre-cracked top plate position and full utilization of a top plate separation layer crack space and is frees of artificial arrangement of a pre-cracking space.