The microstructure transformation, aging hardening behavior and corrosion resistance of 15-5PH stainless steel were studied by XRD, TEM, HRC, polarization curve and electrochemical impedance spectroscopy. The results show that the hardness and corrosion resistance due to Cu-rich phase have coherent orientation relationship with matrix when the aging temperature is lower than 450℃. The Cu-rich phases coarsening and the reversed austenite are observed in the specimen, when the aging temperature reaches to 550 ℃. Moreover, the amount of reversed austenite increases with the increase of aging time. So, the hardness decreases but the corrosion resistance increases. When the aging temperature reaches 620 ℃, the Cu-rich phases exhibit elliptical shape and destroy the coherent relation with the martensite matrix, meanwhile, the reversed austenite continues to increase. As a result, the precipitation hardening effect disappears, however, the corrosion resistance is improved.