Abstract: The relationship between hardness (Rockwell hardness, Vickers hardness and Brinell hardness) and strength (upper yield strength and tensile strength) of steel used for construction steel structure was studied by regression analysis method, the conversion formula and conversion deviation of hardness calculation strength were given, and compared with GB/T 33362-2016 and GB/T 1172-1999. The results show that there was a positive correlation between hardness and strength of steel used for construction steel structure, and the relative deviation of tensile strength converted from Brinell hardness was obviously better than that of Rockwell hardness and Vickers hardness. The tensile strength value converted from Rockwell hardness and the tensile strength value converted from Vickers Hardness given in GB/T 1172-1999 was close to the test result. Considering the existing portable hardness test instruments and sample processing equipment, it was feasible to calculate the steel strength by Rockwell hardness and Brinell hardness in practical engineering.