A novel nickel-based single crystal superalloy with low density had been designed and the creep deformation mechanismsof the experiment alloy under two conditions (1050 °C/200 MPa and 1100 °C/137 MPa) had been systematically discussed. The topological inversion had been observed after fracture under the above two conditions. The effects of temperature andstress on creep life of the experiment alloy had been found no significant difference under the two conditions. It was indicatedthat the small decrease in temperature exerted limited influence on the creep behaviors of single crystal superalloys in therange of high temperature.