Abstract: To investigate the relationship between the chemical composition of 17-4PH steel and the mechanical properties and microstructure of the material, the mechanical properties and microstructure of 17-4PH steel materials with different chemical element contents based on the strengthening mechanism of 17-4PH steel was analyzed. Through experimental observations combined with analytical results, the optimal ratio of alloying chemical composition in a 17-4PH steel material was determined to provide reference data for the alloy design of new precipitation-hardening steels. In order to obtain the mechanical properties of the material with different chemical compositions, it is proposed to determine the optimal content of these alloying elements in 17-4PH steel by using a specific heat treatment with the content of Cr, Ni and Nb elements as a single variable and observing the mechanical properties and microstructural changes of the material when the single variable is a different mass percentage concentration. The results show that a certain content of Cr and Ni elements help improve the tensile strength, yield strength and hardness of the material; Nb elements help improve the corrosion resistance and impact resistance of the material, but Nb is easy to segregation. The comprehensive above can determine an alloy composition of Cr, Ni, Nb elements content of the best content are: Cr14.5wt%, Ni4.4wt% and Nb0.21wt%.