Abstract: Taking SCr430H steel as research object, the effects of different heat treatment processes on the microstructure and hardness of the hardenability alloy structural steel were analyzed. The results show that with the quenching temperature rising from 800℃ to 890 ℃, the microstructure is completely austenitized, and the hardness of SCr430H steel is increased.The hardness reaches the peak value of 40.81 HRC at 860 ℃, and the hardness decreases to 39.86 HRC due to the continuous increase of temperature. When the tempering temperature is 440 ℃, the microstructure is tempered tortenite, and whe n the temperature is above 470 ℃, the microstructure is tempered sortenite, and when the tempering temperature is 500 ℃, α phase recrystallization is obvious, the granular carbide is dispersed. With the increase of the tempering temperature, the hardness of the steel gradually decreases from 36.84 HRC to 29.38 HRC. The optimal heat treatment process is: 860 ℃+heat preservation for 40 min+water cooling quenching, at 500℃+ heat preservation for 40 min+water cooling tempering.