Abstract: In order to investigate the strengthening mechanism and failure of domestic TP310HCbN steel, the microstructure of domestically-made TP310HCbN steel under different stress at high temperature by means of transmission electron microscopy(TEM) and scanning electron microscopy(SEM) is studied. The results show that the precipitates after the creep-rupture test are M23C6 carbides with face centered cubic (FCC) structure located both inside grains and at grain boundaries and NbCrN nitride particles with tetragonal structure dispersed within grains. After long time creep-rupture testing, σ phase precipitated. The hardness of the creep-rupture samples is enhanced due to the dispersed M23C6 and NbCrN particles. M23C6 carbides with lattice parameter of three times of the austenite matrix grow in a cube to cube orientation relationship with the matrix. The amount of M23C6 carbide particles increases with the testing time extended. For the domestic TP310HCbN steel, more attention should be paid to the distribution, size and amount of σ phase and M23C6 during service.