With continuous demands for cost reduction and environmental protection, bainitic forging steels, which have notably higher strength and toughness combination than ferritic-pearlitic forging steels, have been developed and gained an increasingly applications in a variety of critical automotive parts. In order to optimize the microstructure and properties of bainitic forging steel, the influences of tempering temperature ranging from 200 ℃ to 500 ℃ on the microstructure and mechanical properties of a Mn-Cr type bainitic forging steel were investigated based on microstructural observations and mechanical property tests. The results show that the microstructure in the as-forged condition of the tested steel is a mixture of lower lath-bainite and granular bainite. With the increase of tempering temperature (T_temp), the microstructure began to recover and the large blocky martensite/austenite (M/A) constituents decomposed granularly with the precipitation of fine cementites. Further increasing T_temp to 500 ℃, the blocky M/A constituents decomposed completely and the cementites were spheroidized. Consequently, the ultimate tensile strength (UTS) decreases gradually from 1418 MPa of the as-forged specimen to 1094 MPa of the specimen tempered at 500 ℃ with increasing T_temp, while the yield strength (YS) increases gradually with increasing T_temp at first, reaching a peak at 400 ℃, and then decreases with further increasing T_temp. As a result, the yield strength ratio (YS/UTS) increases continuously from 0.73 in the as-forged state to 0.93 of the specimen tempered at 500 ℃. Unlike those of the strengths, the impact energy increases at T_temp of 200 ℃ at first, then it decreases and reaches a valley at 400 ℃, and finally it increases notably again at T_temp of 500 ℃, an increase of about 27% than that of the as-forged one. It is concluded that suitable tempering treatment after forging can obtain better strength and toughness balance of the tested bainitic forging steel, and thus help to expand its application range.