Abstract: To understand the degradation behavior of corrosion resistance in LiOH aqueous solution for Zircaloy-4, Scanning Electron Microscope（SEM） and Scanning Probe Microscope （SPM） are performed to observe the inside and outside surface morphologies of the oxide. Based on the results, it is suggested that there exists compressive stress parallel to oxide/matrix interface in the oxide film because of volume expanding during the oxidation of Zircaloy-4. The oxide film heaves due to compressive stress, which brings strain stress perpendicular to interface, the strain stress leads oxide film break and results in accelerating corrosion rate. The higher the concentration of LiOH aqueous solution is, the quicker the process is.