Abstract: The effects of quenching and tempering at different temperatures on the microstructure and mechanical properties of 30CrMnSiA steel were studied by optical microscope, transmission electron microscope, tensile test and impact test. The results show that the microstructure of 30CrMnSiA steel quenched at different temperatures is a mixture of lat martensite and retained austenite. With the increase of quenching temperature, the martensitic strip bundle of 30CrMnSiA steel gradually widens. 30CrMnSiA steel quenched at 880℃ is tempered at different temperatures. With the increase of tempering temperature, the carbide precipitates in 30CrMnSiA steel increase, and the carbide aggregates in 30CrMnSiA steel tempered at 640 ℃ which are in banded. With the increase of tempering temperature, the strength of 30CrMnSiA steel decreases gradually, while the elongation and energy absorbed by impact increase gradually. The tensile strength, yield strength, elongation and shock absorption energy of 30CrMnSiA steel quenched at 880 ℃ and tempered at 520 ℃ are 1098MPa, 985 MPa, 11.3% and 181 J, respectively, which can meet the performance grade requirements of steel structure fastener materials at 10.9S.