Abstract: Through the field testing and sample testing, safety inspection and life evaluation were carried out on the P91 steel high-pressure main steam piping system of domestic first 9F gas turbine, which had been running for 10 years. The results show that:there were some quality defects existing in the part sections of the high-pressure main steam piping, and the pipes were replaced; the stress of the temperature difference of the high-pressure main steam piping caused by the start-stop process of 9F gas turbine was small and negligible compared with the secondary stress of the piping; the welding joint samples of qualified hardness had a higher endurance strength at 540℃, and the residual creep life was more than 10⁵ h.