The effect of temperature and strain rate on the tensile deformation behavior of GH4151 nickel-based superalloy was investigated via tensile test at temperatures ranging from 400 ^oC to 650 ^oC and strain rates from 0.005 min^-1 to 0.02 min^-1. Then the variation of microstructure and fracture surface was examined to elucidate the deformation mechanisms and fracture features. The results show that the alloy exhibits the Portevin-Le Chatelier (PLC) effect at 400 ^oC, which disappears above 500 ^oC due to accelerated solute atom diffusion. Between 600 and 650 ^oC, the combined effect of γ′ phase hardening and matrix softening results in the tensile strength reaching a peak at 600 ^oC, followed by a decrease at 650 ^oC. At higher temperatures (≥ 600 ^oC), the fracture surface displays “dagger-shaped” shear features, and the increased density of geometrically necessary dislocations (GNDs) at grain boundaries promotes intergranular cracking. Higher strain rates (0.02 min^-1) enhance work hardening and local strain concentration, while lower strain rates (0.005 min^-1) facilitate more uniform plastic deformation. This research provides a good reference for optimizing the microstructure control and engineering applications of GH4151 alloy.