Abstract: Comparative analysis was conducted on the microstructure and properties of 4Cr5Mo2V steel and 4Cr5MoSiV1 steel using methods such as metallographic examination, impact testing, scanning electron microscopy, and energy spectrum analysis. The phase diagrams were simulated and calculated using software. The results show that the V element content of 4Cr5Mo2V steel was lower than that of 4Cr5MoSiV1 steel, while the Mo element content was higher, which changed the stability of the MC phase in the steel. The dissolution temperature and content of high melting point MC phase precipitated carbides in 4Cr5Mo2V steel were lower than those in 4Cr5MoSiV1 steel, which increased the impact toughness of 4Cr5Mo2V steel.