Abstract: Welding process of 60 mm thick SA508-3 steel pipe which is firstly used in nuclear power was simulated by ANSYS to obtain the temperature field and the residual stress.Simulated thermal and mechanical results were compared with the experimental results in the same welding parameters.It was found that the residual stress distribution is close to the measured values.During welding,the peak temperature exists in the centre of the heat source and its vicinity where the temperature gradient is much larger.However,the temperature descends sharply away from heat source.The residual stress on the outer surface of pipe are greater than that in the inner surface,of which the tensile residual stress in the welding zone and adjacent zone are largest,and gradually decreases away from the welding zone.The residual stress in the middle of cylinder is opposite to that in the two longitudinal ends.These results provide theoretical knowledge for the control of welding residual stress of pipe.