The effects of quenching temperature, cooling method and tempering temperature on the microstructure and mechanical properties of 38CrMoAlA steel have been studied through a series of heat treatment process tests. The experiment has measured the mechanical properties of the steel in different heat treatment conditions. The mechanical tests include tensile, impact and hardness test. The experiment has also measured the continuous cooling change curve of the steel, and analyzed the microstructure of the steel under different cooling rate and different temper conditions. The results of tests show that the effect of quenching temperature on mechanical properties of the steel the impact is not big when quenching at the temperature between 900℃ and 1000℃. Because of different cooling intensity of quenching medium, different cooling methods lead to different microstructure, and thus affect the mechanical properties of the steel. The effect of tempering temperature on the microstructure and mechanical properties of the steel is the most remarkable. When tempered at the temperature between 100℃ and 400℃, it behaves temper brittlement. While tempered at about 620℃, it can get a good combination of strength and toughness. Therefore, choosing the heat treatment process of quenched by heating to 940℃, holding at temperature for one hour, cooling in oil, and tempered by heating to 620℃, holding at temperature for five hours, cooling in oil, 38CrMoAlA steel can get the best property.