Abstract: Zr-0.2Cu-xNb (x=0.2, 0.5, 1.0, 2.5) alloys were prepared by vacuum β-phase oil quenching, cold-rolling deformation and annealing. The superheated steam corrosion test was carried out in a static autoclave. The microstructure of the alloy and the oxide film formed by corrosion was studied by scanning electron microscopy and transmission electron microscopy. The results show that with the increasing of Nb content, the number of Zr2Cu phases in Zr-0.2Cu-xNb alloys decreases gradually, while the number of β-Zr phases increases gradually. The second phase of Zr2Cu with small size is beneficial to corrosion resistance. The β-Zr second phase promotes the generation of micro-cracks in the oxide film during oxidation and reduces the corrosion resistance of the alloy. When the Nb content in Zr-0.2Cu-xNb alloy is close to its maximum solid solubility in α-Zr, the alloy has the best corrosion resistance.