Density-functional theory calculations are carried out for a biomimetic dimanganese complex, [H2O(terpy)-MnⅢ(μ-O)2MnⅣ(terpy)OH2]3+(1, terpy =2,2:6,2″-terpyridine), which is a structural model for the oxygen evolving center of photosystem Ⅱ.Theoretical investigations aim at elucidating the asymmetry features in the geometric and electronic structures of complex 1, as well as their influences on the chemical functions of the two manganese centers, in the presence of water solvent.