Abstract: In the inspection of power plant boiler, the Leeb hardness detected on site is usually converted into Brinell hardness. However, the existing conversion relationship does not make a detailed distinction between different materials, and the range of hardness is not wide enough. The end-quenching and integral heat treatment experiments of P22 steel were carried out. The hardness values of Leeb and Brinell with wider hardness range and more uniform distribution were obtained, and then the conversion relationship between Leeb hardness and Brinell hardness was established. The results show that there was a quadratic regression relationship between the Leeb hardness and Brinell hardness, and the conversion relationship is H_BW=0. 001 6H_LD²-0. 66H_LD+155. 7.