Abstract: The existing form of niobium in zirconium-based alloy containing Fe, Sn, Cr alloying elements was researched qualitatively by means of SEM. The results show that most parts of niobium together with Fe, Cr forms in LAVES precipitate firstly, and the solubility of niobium in α-Zr is lower than 100 μg·g -1. Combining with the previous research of Nb on out-of-pile corrosion resistance, the relatively higher content of Nb is beneficial to improving the resistance in lithiated water, but harmful to the resistance in steam in autoclave test. It is suggested that the study on the influence of intermediate annealing on content of Nb both in α-Zr and in LAVES precipitate is very important to research the corrosion mechanism.