Abstract: By using rapid phase transition instrument, X-ray stress analyzer and MTS material testing machine, etc., aging tests were conducted on steel 05Cr17Ni4Cu4Nb at different temperatures, so as to measure the reverted austenite content, and to analyze the changes of reverted austenite content in the steel after being aged at 605℃ for different holding time, and under tensile deformation conditions. Results show that when the aging temperature is lower than the A_c1 of material, the content of reverted austenite would increase with the rise of aging temperature; whereas when the aging temperature is higher than the A_c1, the content of reverted austenite would reduce instead, due to the occurrence of martensite transformation in the cooling process. For the steel being aged at 605℃, the content of reverted austenite first increases and then decreases with the rise of holding time, and in the increasing process, the precipitation behavior of reverted austenite complies with JMA kinetic equation. Phase transformation of reverted austenite happens in the deformation process, and the logarithm value of the ratio of reverted austenite content before and after deformation is in good linear relationship to the true strain.