Abstract: Scrapped AISI 321 stainless steel with a large number of σ precipitated phases after serving for 80 000 hours at 700 ℃ was treated by different solid-solution treatment processes to study the microstructure and high-temperature mechanical properties of the stainless steel before and after solid-solution treatment and the focuse was on the recovery of microstructure and high-temperature mechanical properties after solid-solution treatment. The results show that solid-solution treatment could make σ phase dissolved and eliminated. After solid-solution treatment at 1 050 ℃ for 2 h, the microstructure and the high-temperature mechanical properties of the stainless steel got a good recovery and complied with the performance requirement of industry standard, and the solid-solution process was a best route to recover the microstructure and properties of AISI 321 stainless steel.