Abstract: 10Ni5CrMoV steel is a high strength low alloy steel (HSLA), its solid-state phase transformation effects cannot be ignored in welding mechanical analysis. In this study, welding numerical simulation is conducted with consideration of solid-state phase transformation effects including volumetric change and hysteresis of yield strength. The results show that longitudinal tensile stress become much lower in phase transformation zone, but it maintains high stress level in adjacent areas. Nevertheless, the distribution of transverse stress is changed a lot, with a similar peak value, approximately 25% of yield strength at room temperature. And it is approved that both longitudinal and transverse residual stress are in good agreement with experimental measurements.