Enhancement of magnetoresistance (MR) has been achieved at room temperature in the perovskite La 0 . 8 Ba 0 . 2 MnO 3 epitaxial thin films. It was found that these particular epitaxial thin films exhibit higher MR ratio than that of bulk material (21% at 270K), i.e. 33% at 320K for 400 9 thickness, 43% at 307K for 650 9, 45% at 298K for 1000 9 and 48% at 267K for 1300 9 under the magnetic field of 8000Oe. The metal-insulator transition temperature and magnetoresistance strongly depend on the film thickness. The MR ratio of the La 0 . 8 Ba 0 . 2 MnO 3 film at room temperature is remarkably large in comparison with that of other magnetoresistive oxides.