Abstract: Solid solution treatment at 930 ℃ for 1 h and following by aging at 480,510,540,565,590,620 ℃ for 4 h were carried out to study the effects of aging temperature on microstructure and mechanical properties of PH13-8Mo stainless steel. The results show that, PH13-8Mo stainless steel had better comprehensive mechanical properties, such as the highest hardness and strength and enough impact toughness, after aging at 510 ℃. When aging at 510-620 ℃,the hardness and strength decreased and impact toughness increased with the increase of aging temperature. PH13-8Mo stainless steel began to precipitate the intermetallic compound Ni3Al when aging at 480 ℃, and the precipitates gradually grew up and increased in number gradually with the increase of aging temperature.