In this paper, a series of ITO thin films with different concentrations of metal Sn doping were prepared by electron beam evaporation technique. X-ray diffractometer, atomic force microscope, UV-Vis-NIR spectrophotometer, four-probe resistivity meter and Z-scan system were used to measure and characterize the physical phase structure, microscopic morphology, optical absorption, square resistance and nonlinear optical properties of ITO films, respectively. The test results show that, with the increase of metal Sn doping concentration from 10% to 30%: the crystalline quality of the ITO film is enhanced; the surface roughness of the film increases and the grain size gradually increases; the plasma absorption is enhanced and the position of the absorption peak is red-shifted and the optical band gap is narrowed; the square resistance of the film continuously reduces; the nonlinear absorption coefficient gradually increases, and the maximum absolute value can be increased to 2.59× 10-7 cm/W. The finite-difference fitting results in the time domain show that the variation pattern of electric field intensity of ITO thin film samples with different metal Sn doping concentrations is consistent with the experimental results.