The purpose of this article is intended to study the fracture toughness of anisotropic nickel-based single crystal superalloys at elevated temperature by compact tension (CT) specimen in experiment method. The special attention is put on the orientation and temperature dependence of mechanical properties of single crystal as well as thickness effect of specimen. The experimental results show that crystallographic orientation and temperature have much complex effect on fracture toughness. The difference of fracture toughness of single crystal for different crystallographic orientation at low temperature is much greater than that at high temperature. The nickel-based single crystal specimen may merely become less anisotropic with the increase of the ambient temperature seems as more multi-slip action appears. The fracture mode of the specimens transfers from brittle to ductile as the temperature increases; also, the fracture toughness of single crystal for the same orientation becomes larger with the decreasing of the thickness of single crystal specimen.