Abstract: Different forging and heat treatment tests of 4Cr5MoSiV1 die steel were carried out. The effects of different forging and heat treatment processes on the microstructure and properties of 4Cr5MoSiV1 die steel were studied by means of microstructure observation, hardness test, impact test and impact fracture observation. The results show that when the4Cr5MoSiV1 steel is subjected to 1250 ℃ high temperature homogenization treatment, after forging, it is subjected to 1100 ℃×2h high temperature heat preservation treatment, and then is subjected to 850 ℃×2 h+730 ℃×2 h isothermal spheroidizing annealing, the structure is small equiaxed ferrite, and spherical carbides are round in size and uniformly distributed, without obvious secondary carbides. Its hardness is 210.3 HB, the impact absorption energy is 29.5 J, and its overall performance is the best.