We report on the study of the transport property of La-doped SrTiO 3 thin films grown by pulsed laser deposition (PLD) method under the oxygen pressures of 0.1 Pa, 1 Pa and 10 Pa. With the increase of oxygen pressure, resistivity of the samples is enhanced markedly. A metal-to-insulator transition appears in all the films at low temperatures. The Hall effect has been studied to obtain the information on carrier density and Hall mobility. An electron-like character and temperature-dependent carrier density have been found. It shows a monotonic decrease with the increase of oxygen pressure. This phenomenon can be ascribed to the cation vacancies induced by excessive oxygen in the films. The Hall mobility also exhibits obvious dependence on oxygen pressure. Due to the inelastic scattering strength of electrons, the transport behavior in metallic region can be described by the T2 law or small-polaron coherent conduction model.