Objective To establish 5 different finite element models of the proximal femur based on CT images, and analyze the influences of element size on materials distribution and biomechanical behavior of the proximal femur model. Methods The proximal femur was scanned by spiral CT. The images, stored as DICOM format, were extracted by Mimics to obtain 3D geometric data, and then meshed separately by Mimics, 3-Matic and ICEM software to establa voxel element model, a tetrahedral element model and 3 hexahedral element model (with element size of 2, 1, 0.5 mm). These meshed models were assigned materials by Mimics, and their mechanical behavior was analyzed by Abaqus eventually. Results For the proximal femur model with material assignment based on CT images, the influence of element size on the total mass of all the 5 models was not significant. The nodal Mises stress and nodal displacement along the same path in 5 models showed a similar tendency, while the Mises stress at each node displayed an obvious deviation. The nodal Mises stress in the hexahedral element model with the element size of 0.5 mm showed accordance with the voxel element model. Conclusions The element size has a small influence on the total mass and nodal displacement when the material assignment is attributed to the model based on CT gray values, while decrease in the element size will affect the materials distributions and stress distributions of the model. When the element size of the proximal femur model is close to its voxel size, the mass distributions and mechanical behavior of the femur can be preferably reflected.