Numerical simulation of arc welding and post-weld heat treatment of TC17 titanium alloy plate was carried out, the phase transformation and creep of materials were considered in the model, evolution of temperature field during welding and heat treatment and the distribution of residual stress before and after heat treatment were obtained. Results show that, due to the large heat input, large residual stress is generated after welding, the longitudinal residual tensile stress in the HAZ zone near the welding seam reaches about 650MPa, and it decreases to about 160MPa after heat treatment. Residual stress was measured by blind-hole method and X–ray diffraction. The calculated residual stresses are in good agreement with the measured results of the blind-hole method.