The phase diagram of superaustenitic stainless steel 654SMO was calculated by thermodynamic software and the precipitated phases in the specimens aged at 800-1100°C for 1hwere studied by methods of physicochemical phase analysis,scanning electron microscopy and transmission electron microscopy.The results showed that the size of precipitated particles increased with increasing the temperature.The amount of second phases reached the maximum value at 900°C,but decreased above 900°C.There were about eight kinds of precipitated phases in 654SMO includingσphase,Cr_2N,μphase,χphase,Laves phase,M_(23)C_6,M_6C and M_3C,in which theσphase and Cr_2N were the dominant precipitated phases. The phase diagram of superaustenitic stainless steel 654SMO was calculated by thermodynamic software and the precipitated phases in the specimens aged at 800-1100 ° C for 1 hwere studied by methods of physicochemical phase analysis, scanning electron microscopy and transmission electron microscopy. The results showed that the size of precipitated particles increased with increasing the temperature. The amount of the second phases reached the maximum value at 900 ° C, but decreased below 900 ° C. There were about eight kinds of precipitated phases in 654SMO including σphase, Cr_2N, μphase, χphase, Laves phase, M_ (23) C_6, M_6C and M_3C, in which thephase and Cr_2N were the dominant precipitated phases.