Base on finite element method, the stress field evolution of zirconium alloys with different oxidation degrees during the Loss of Coolant Accident process is analyzed in this paper, in which the Zr-4 cladding with three-layer structure after Loss of Coolant Accident process has been modeled, with representing different oxidation degrees of the zirconium alloy cladding by the volume fraction of α-Zr (O). The simulation of two-step cooling from 1200 ℃ to 800 ℃ then to room temperature is carried out. The results show that the stress in the oxide film is compressive stress, and the stress gradient of oxide film with the decrease of temperature is the largest, which leads to a larger residual stress at the interface between α-Zr (O) layer and matrix, and the larger the proportion of matrix volume, the smaller the internal residual stress after cooling. In the low oxidation model, the stress of α-Zr (O) layer is basically unchanged at the end of cooling,。However, there is obvious stress concentration when the oxidation degree is higher. The larger compressive strain has been produced in the high oxidation degree model, which leads to greater deformation of the matrix when cooling down. Accordings to the analysis on the corresponding constitutive equations of each structure in different oxidation degree models, it is found that the stress of each layer in the early stage of quenching decreases first and then increases. There is difference of mechanical properties between the matrix close to the edge of α-Zr(O) layer and that close to core structure. For the model with higher oxidation degree, the core compressive stress of matrix structure is higher than that of edge structure under the same strain.