The hot compression deformation of GH79 superalloy were investigated systematically on a Gleeble-3800 thermal simulating tester. Based on the hot compression test behavior and mechanism on high temperature deformation behavior and microstructure evolution, the variation of strain rate sensitivity exponent m, activation energy Q and grain size exponent P values at different strain rates and different temperatures were obtained. The dynamic DMM hot processing map based on different instability criteria was drawn while the deformation mechanism maps incorporating dislocations the inside grains were obtained. The processing map was used to analyze the processing instability regime and appropriate processing regime. With the deformation mechanism maps, the Burgers vector compensated grain size, the dislocation evolution rule at modulus compensated flow stress and the modulus compensated stress and the dislocation quantities of GH79 superalloy at different temperatures, the hot deformation mechanisms were elucidated.