We report on epitaxial growth and magnetic properties of Mn2.5 Ga thin films, which were deposited on Cr/MgO single crystal substrates by magnetron sputtering. X-ray diffraction results revealed the epitaxial relationships as Mn2.5 Ga (001)  Cr (001)  MgO (001) . The presence of (002) and (011) superlattice peaks indicates that the films were crystallized into DO22 ordered structures. The perpendicular magnetic anisotropy (PMA) properties were found to be related to the extent of DO22 chemical ordering. A giant PMA (Ku eff =1.2× 107 erg/ cm3) and low saturation magnetization (Ms =250 emu/ cm3) can be obtained for the film with highest chemical ordering parameter (S=0.8).