Special welding simulation soft SYSWELD is applied to simulate temperature field and stress field of multi-layer multipass welding for dissimilar metals in casing pipe structure,and the metallographic section observation and X-ray diffraction stress test are used to check the simulation model. The results show that the weld section obtained by simulative welding temperature field of checked model is consistent with the actual weld section,the temperature of the root joint fluctuates 14 times over time,each fluctuation has two peaks;simulation results are basically same with residual stress measured by X-ray diffraction,the distributions of axial residual stress at different welding position demonstrate similar regulation,axial residual stress at welding position of 0 degree and 90 degree are much higher,and the maximum residual stress is close to 300 MPa;numerical valves and distribution of circumferential residual stress at different welding position are same,the maximum circumferential residual stress is close to 300 MPa at 15 mm away from the root of first weld;the maximum Von Mises stress appears in the heat affected zone of low alloy steel,and the maximum Von Mises stress at welding position of 90 degree is 377 MPa.