Abstract: Solid-solution treatment was carried out on PH13-8Mo high strength stainless steel at 925℃, and then aging treatment was carried out at 510,540,550,565℃and 595℃ to study the type and content of precipitated phases and the effect of precipitated phase on mechanical properties of the tested steel. The results show that the precipitated phase in the tested steel mainly is M₂C after aging at lower temperature, the precipitated phases are M₂C, M₂₃C₆, Ni₃Al and NiAl after aging at intermediate temperature, and the main precipitated phases are NiAl and M₂₃C₆ after high temperature aging.With the increase of aging temperature, the precipitated phase's content increases, and tensile strength and yield strength of the tested steel gradually decrease, while ductility and toughness continuously improve. The precipitated second particles during aging can impede dislocation movement, and thus increase strength of the tested steel.The optimum comprehensive properties can be obtained for the tested steel after quenching at 925℃ and then aging at 540℃.