The hardness change and microstructure evolution of high cobalt molybdenum stainless bearing steel after quenching at 1050 °C, 1050 °C, 1100 °C were studied by hardness tester, scanning electron microscope, metallographic microscope, and X-ray diffractometer. The results show that the high cobalt molybdenum stainless bearing steel's hardness, tensile strength, and yield strength increase with the temperature. Through the scanning test, the rise in quenching temperature makes some carbides dissolve. Metallographic analysis shows that increased quenching temperature dissolves some carbides, loses the pinning effect, and increases the grain size. XRD test analysis shows that retained austenite (RA) content increases with quenching temperature. Therefore, the increase in quenching temperature will lead to the strength and hardness of the sample decreased. Consequently, it is necessary to control the quenching temperature of the sample within the appropriate range to obtain the best performance.