Abstract: Through heat treatment test,residual stress test,tensile test,bending test,hardness test and other methods,the effect of simulated post-weld heat treatment temperature on the welding residual stress and mechanical properties of Q345R steel plate welded joint was analyzed.The results showed that as the simulated post-weld heat treatment temperature increased from 400℃ to 620℃,the welding residual stress of Q345R steel plate welded joint gradually decreased,and the welding residual stress could be basically eliminated after heat treatment at 620℃.With the increase of post-heat treatment temperature,the tensile strength and hardness of Q345R steel plate welded joint decreased.The hardness of the heat-affected zone decreased most obviously,followed by the hardness of the weld,and the hardness of the base metal remained basically unchanged.