The hot deformation behavior and microstructure evolution of TC17 alloy were investigated by hot compression tests at 700–950 ℃ with strain of 0.9 and strain rate of 0.001–10 s-1. A modified Arrhenius-type constitutive equation was established to describe the hot deformation characteristics. The spheroidization process of α phase was studied by scanning electron microscopy. The results show that the lamellar α phase forms a groove through the boundary splitting mechanism, and the gradually deepened groove eventually leads to the splitting of the lamellar α phase, and then diffuses to the surrounding under the termination migration mechanism. Finally, the lamellar α phase spheroidizes. The microstructure evolution during hot compression was analyzed by electron backscatter diffraction technique. The results show that the spheroidization of lamellar α phase is the main softening mechanism of TC17 alloy at low temperature. With the increase of temperature, dynamic recrystallization gradually transforms into the main softening mechanism of TC17 alloy. At the same time, the discontinuous dynamic recrystallization at the subgrain boundary and the continuous dynamic recrystallization at the subgrain rotation of TC17 alloy were found.