Abstract The influences of applied stress (120–760 MPa) and temperature (700–1000 °C) on the creep deformation mechanisms of the newly developed nickel-base superalloy M951G have been studied. The dominant deformation mechanisms of M951G alloy after different creep tests were systematically investigated and the reasons for their transition were well discussed. A creep mechanism map at various creep conditions was summarized and the theoretical critical resolved shear stresses (CRSSs) of various creep mechanisms under different temperatures were also calculated. Results show that the CRSSs of different creep mechanisms display different dependencies of temperature and the favorable deformation mechanisms at different creep conditions are different. τ APB , τ OB and τ CL are decreased to varying degrees with the temperature increasing; on the contrary, there is a positive correlation between τ SF and temperature. At low temperature region, the favorable deformation mechanism is shearing of γ′ precipitates by stacking faults. However, it changes to antiphase boundaries (APBs) coupled dislocation pairs shearing in the γ′ precipitates and dislocation climbing in the γ matrix channel at high temperatures. At intermediate temperatures, both stacking faults and APBs are observed owing to the alternate leading of the CRSSs for APBs and stacking faults shearing in γ′ precipitates.