Indium-tin oxide (ITO) thin films are deposited by electron beam evaporation and treated by rapid thermal annealing (RTA) under nitrogen. The influences of RTA treatment on crystal orientation, microstructure, composition and photoelectric properties of ITO thin films are measured by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), visible spectrophotometer and four-probe meter. The analysis results show that the rise of annealing temperature is helpful for Sn to release electrons on the 5s orbit, and Sn4+ to replace In3+ to form a new chemical bond. Moreover, the binding energy of In and Sn elements is increased, their degree of oxidation is changed, and the electron carrier concentration and mobility are increased. Besides, the crystal lattice distortion of ITO thin films, the defect density and compactness are ameliorated, and the recovery of the lattice mismatch is promoted. In the experience of 450 ℃ RTA, preferable photoelectric properties of ITO thin films can be obtained.