Abstract: 17-4PH steel is a typical martensitic precipitation hardening stainless steel with high strength, toughness, and good corrosion resistance. After solid solution treatment at 1040℃, 17-4PH steel was subjected to primary aging treatment at 480℃ and 550 ℃, as well as secondary aging treatment at 550℃ after 480℃ aging. The mechanical properties and metallographic structure of the material under different heat treatment states were tested. The experimental research results show that the metallographic structure of 17-4PH steel after solid solution treatment and aging at 480℃ is martensite, while the metallographic structure after aging at 550℃ is tempered martensite. 17-4PH steel has the highest tensile strength and yield strength, but lower impact toughness when aged at 480 ℃. As the primary aging temperature increases, the strength of the steel decreases and the impact toughness increases at 550℃. 17-4PH steel can achieve good comprehensive mechanical properties such as strength and impact toughness under solid solution at 1040℃ and aging at 550℃.