The utility model discloses a tool for adjusting the water pressure of a primary circuit of a pressurized water reactor nuclear power plant. The tool comprises a circular handle, a plurality of spokes and a hexagonal sleeve, wherein the spokes are radially and fixedly arranged on the inner side of the circular handle; the hexagonal sleeve is fixedly arranged at the junction of the spokes and is concentric to the circular handle; a plurality of scale lines uniformly distributed along the circumference are arranged on the end face of the circular handle. Due to the fact that the circular handle is arranged and a user needs to hold the circular handle with both hands for rotation adjustment, the rotation stability is improved; meanwhile, the water pressure of the primary circuit can be accurately adjusted to be maintained to be about 228bar; moreover, the adjusting tool is fixed on an adjusting valve of a water pressure test pump through the hexagonal sleeve, so that the problem that the adjusting tool is disengaged is avoided.