This work reports the magneto-anisotropy property of epitaxial Fe3Si film grown on GaAs (0 0 1) substrate by molecular beam epitaxy (MBE). We present a strong dependence of anisotropic magnetoresistance (MR) on field in the Fe3Si film plane. The electron transport behavior is highly dependent on the direction of the current either parallel or perpendicular to the magnetic easy axis. By altering the direction of current from magnetic hard axis to magnetic easy axis, the unconventional behavior switches to normal anisotropic magnetoresistance (AMR). In addition, the anisotropic behaviors were also observed from the magneto-optic Kerr effect (MOKE) measurement, which demonstrates unusual anisotropic properties with the crystalline anisotropic constant K1¼(3.870.2) 104 erg/cm3 and uni-axial anisotropy Ku¼(1.270.04) 104 erg/cm3. The ratio K1/Ku was used to account for the MR.