Abstract: The effects of quenching temperature and tempering temperature on the microstructure and hardness of high vanadium high speed steel(HVHSS) were investigated.The results show that with the increase of quenching temperature,the hardness of the steel first increased when the quenching temperatuive lower than 1 040 ℃ and then decreased when the quenching temperature higher than 1 040 ℃.With the increase of quenching temperature,carbide in the microstructure decreased,martensite became coarsing and residual austenite increased.With the increase of tempering temperature,the hardness of the steel had no obvious change when the tempering temperature lower than 500 ℃,but when the tempering temperature higher than 500 ℃,the hardness first increased and then decreased and reached a peak value at 520 ℃.With the increase of tempering temperature,disperse carbides precipitated from the martensite gradurally and grew up together,and at the same time martensite and partial residual austenite transformed into tempered martensite.