In this paper the characteristic of ZrO2 grain growth during the oxidation in nanocrystalline Zr-4 under 673 K/10.3 MPa conditions was studied. The results show that the grain size and grain growth rate of ZrO2 which formed on the nanostructure basis were smaller than that of ZrO2 formed on the coarse grain basis. So the nanocrystalline treatment leads to fine grain of ZrO2 and has influence on the oxidation dynamics of zircaloy-4