Abstract: The effects of different temperatures and holding time quenching on the microstructure and mechanical properties of 4Cr2Mn2Mo die steel were studied by OM, tensile test and hardness test. The quenching test of test steels（400-560） ℃×2 h,480 ℃×（0.5-3） h was carried out. The results show that with the increase of quenching temperature, in the test steel, the slab martensite increases first and then decreases, and the acicular martensite decreases first and then increases.480℃ quenching, the content of lath martensite is the most, the needle martensite is the least. The elongation of 480 ℃×2 h quenching test steel is 7.4%, which is obviously higher than that of other quenching test steel. At the same time, the intensity is at a higher level. The optimum quenching process of the test steel is 480 ℃×2 h.