Sol-gel method was used to prepare La3+-doped TiO2 Nanopowders. The sample was characterized with XRD, TEM, HRTEM, STEM-EDS, XPS and ultraviolet-visible (UV-Vis) spectroscopy. The changes of the La3+-doped TiO2 in the phase transition were discussed on the aspects of its phase composition, the average grain size, the microstructure, the chemical states and UV-Vis absorption spectroscopy. Doping with La3+ significantly suppressed the phase change and grain growth of TiO2. It effectively improved the TiO2 dispersibility and reduced the average particle size of TiO2. With the increase of the calcination temperature, the second phase La4Ti19O24 gradually precipitated from the La3+-doped TiO2 and formed an incoherent interface with the Brookite TiO2 phase, which precipitated in the form of irregular spheres from the surface of the TiO2 base. Secondary phases are originated from segregation of point defects at grain boundaries in La3+ doped TiO2. The segregation driving force is mainly the elastic strain energy. With the increase of calcining temperature, the atomic percentage of the O1S in the La3+-doped TiO2 gradually decreased, and that of the La3d gradually increased. There was an energy loss peak at the higher binding-energy side of the main peak of the La3d, and Ti3+ existed after the calcination. La3+ Doping makes the optical absorption bandedge of the TiO2 red-shifted. But with increasing calcination temperature, the optical absorption bandedge was blue shifted.