Abstract: Based on constitutive relationship of thermal viscoelastic integral-mode,considering the properties of material,which depend great on temperature fluctuation and the effect of phase-transition latent heat,heat-force coupling function and load step character of ANSYS were employed to simulate the hot-plate welding procedure of high-density polyethylene(HDPE) plastic pressure pipe.The finite-element analyses on stresses distribution of welded joint was conducted,and transient stresses distribution pattern in axial,radial,and circumferential directions were obtained.Residual stresses was measured by the mathar method and the sachs method,and it showed that the actual measured results of the residual stresses are basically coincident with the results of numerical analysis.