Abstract: The effects of cold straightening on the mechanical property of pressure vessel steels were discussed by means of chemical composition analysis, residual stress test and mechanical property test. The results show that after cold straightening, the yield strength of the samples increased, and the tensile strength, elongation and shrinkage were basically unchanged. After the samples were cold straightened and annealed, both the yield strength and the tensile strength decreased, and the elongation and shrinkage were basically unchanged. The main reason for the cold straightening affecting the mechanical property of pressure vessel steels was that the residual stress produced and the strain hardening appeared after cold straightening, which increased the yield strength of the material.