Abstract: In order to research the microscopic behavior of Si atom adsorbed on CeO₂(111) surface, the adsorption, electronic structure and diffusion behavior of Si atom on CeO₂(111) surface were studied using the first principle method. The adsorption energy was calculated. The electron states density, charge density distribution, diffusion activation energy of the most and sub-stable adsorption sites of Si atom on the CeO₂(111) surface were also calculated. The results show that Si atom is most easily adsorbed on the surface layer of O atoms, in which the O bridge site (O_bri) has the strongest adsorption, and the adsorption strength at the O top site (O_t) and the O three-fold site (O_h) is second. Si atom only has a great influence on the structure of the nearest surface of O atoms, which is consistent with the increase of the charge density overlap between the Si atom and its nearest neighbor O atoms. The Si atom most easily diffuses from the O_bri site to O_h site while around the O_t site, and the required activation energy for diffusion is 0.849 eV.