Abstract: The inverse-welding method, post welding cooling treatment(PWCT) to eliminate residual stress, was analyzed by deactive element method using commercial finite element code ABAQUS. The residual stresses eliminated in post welding cooling treatment of P122 steel were quantitatively analysed with different heat treatment temperatures, the cooling media, the cooling rates and cooling times. Results show that both the Mises residual stress and transverse residual stress were reduced obviously after PWCT. And the effect of heat treatment temperature on PWCT method was the most remarkable. Then the effects of cooling time, cooling rate of cooling medium during the PWCT were reduced sequentially. When the heat treatment temperature is 400 ℃, the cooling time is 20 s, this method could not only eliminate the welding residual stress but also form compressive stress layer of 1.3 mm depth in the surface of the treatment.