Abstract: Based on the initial ellipticity of the oil field casing and the non-uniform external load, the finite element analysis model of the casing was established by ANSYS. The non-uniform load combinations with different uniformity coefficients were selected to study the stress distribution law and the variation of the stress value under different ellipticity. The simulation data were compared with those of the ideal circular casing. The study results show that the size of the casing stress and the distribution of stress are related to the size of the initial ellipticity and the uniformity of the non-uniform load. When the casing's ellipticity increases, or the uneven degree of the load decreases, the maximum stress value of the casing increases, and the distribution of the stress is increased. It should be reasonable to control the size of the ellipse to improve the strength of the casing.