Abstract: The effects of aging treatment at different temperatures and following low-temperature treatment on the content of reverted austenite and hardness of 04Cr13Ni8Mo2Al steel were studied with rapid phase transition instrument,X-ray stress analyzer, optical microscope and hardness tester. The results show that the starting temperature of martensite transformed to austenite (A_c1) of the tested steel was 620℃, and the finishing temperature of martensite transformed to austenite (A_c3) was 675℃. With the increase of aging temperature,the content of reverted austenite remained constant first,then increased rapidly, and then decreased rapidly. The reverted austenite content reached the maximum of 35vol% at aging temperature of 620℃. The Vickers hardness decreased at the aging temperature below A_c1 with the increase of aging temperature, increased slightly at the aging temperature over A_c1 because of the formation of martensite, and decreased slightly at the aging temperature close to 700℃. After low-temperature treatment, the Vickers hardness of the aged test steel increased, the content of reverted austenite decreased, and the variation amount of reverted austenite content before and after low-temperature treatment increased with the increase of aging temperature.