Abstract: The possibility of friction welding of high-speed steel to 45 steel below the phase transformation temperature of high-speed steel has been studied in this paper by utilizing superplasticity of high-speed steel and controlling the braking course in friction welding. The metallographic examination of joint in different welding temperature proves that the joint metal on the side of high-speed steel has a gentle structure slope at the 800℃.Examination of joints at different welding temperature show that the joint at 800℃ has the same mechanical property as the base metal,an even hardness distribution,and no hardness pinnacle appeared as opposed to the case appeared above the phase transformation temperature.