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 (Ac1) of the tested steel was 620℃, and the finishing temperature of martensite transformed to austenite (Ac3) 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 Ac1 with the increase of aging temperature, increased slightly at the aging temperature over Ac1 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.