Abstract: The effects of deformation temperature (1100-1500 ℃) on the mechanical properties and microstructure of Nb521 alloy were analyzed and the tensile test at high temperature was carried by using ultra-high temperature mechanical test system.The results show that the flow stress of Nb521 alloy decreases with the increase of deformation temperature, indicating that the strength decreases, while the elongation increases.When the deformation temperature reaches 1300 ℃, the mechanical property of Nb521 alloy changes significantly, which is due to the dynamic recrystallization occurs in the alloy, and the nucleation mode is the bulge nucleation at the grain boundary.As the deformation temperature continues to increase, the microstructure changes from the original flat structure to the equiaxed structure.When the temperature reaches 1500 ℃, the complete recrystallization occurs.A large number of equiaxial dimples appear on the surface of Nb521 alloy at high temperature, which shows a ductile fracture mechanism.