Abstract. In this lecture, the hot deformation, cold deformation and hardening behavior of Nb521 niobium alloy were studied by means of hot compression experiment, EBSD, TEM and universal testing machine. The deformation constitutive equations and microstructure evolution laws of cold deformation and hot deformation of Nb521 niobium alloy were obtained. The results show that the thermal deformation of the alloy is mainly dynamic recovery, and the dynamic recrystallization occurs at the strain rate of 0.001 s-1 and the deformation temperature of 1400~1450℃, and the grain grows with the increase of the deformation temperature. The strengthening effect of cold deformation on Nb521 sheet is very significant, especially at the initial stage of deformation, and then with the increase of deformation, the strengthening effect gradually weakens. For the fitting analysis of the cold-deformation stress-strain curve of Nb521 alloy, Ludwigson model is suitable for regression analysis of 0%, 10% and 30% deformation of Nb521 sheet, while Hollomont model is suitable for regression analysis of 50% deformation.