Abstract: The microstructure and mechanical property of T92 steel post welding has been studied through stimulating work condition. The conclusion shows that the hardness of weld joint and tensile strength of base metal fall down with the rise of the temper temperature,quenching martensite has coarse needle-like character. When tempered between 740~780 ℃,the martensite structure became fine and has apparent lath character,tempered above 780 ℃,the martensite lath character disappear and the weld joint show troostitic structures. The carbide in the tempered martensite of base metal will aggregate and ferrite content percentage increases with temper temperature arise. It can satisfy the requirements of ASME when temper under 780 ℃.