Abstract: In order to better understand the effect of PWHT (post weld heat treatment) on SA517 Gr.F quenched and tempered steel welded joint, the mechanical properties and microstructure distribution characteristics of SA517 Gr.F welded joint by SMAW (shielding metal arc welding) before and after PWHT were compared and analyzed. The analysis results show that, compared with that of as-weld welded joint, both the room temperature and 360℃ high temperature tensile properties of the welded joint decrease, and the peak micro-hardness of weld metal and HAZ also decrease after PWHT. The residual stress of the welded joint is decreased by PWHT, however, the impact properties of the weld and HAZ are not improved. It is suggested that PWHT can be exempted for SA517 Gr.F quenched and tempered steel if the requirements of ASME Code Case N-71-18 can be satisfied.