The theoretical study on magnetostructural correlation in unsymmetrical Cu(II) binuclear complexes bridged by [C2O2(NH)(2)](2-) has been performed using the broken symmetry approach within the framework of density functional theory (DFT). The calculated results show that the magnetic coupling interaction decreases with the changes of the coordination environment around the Cu atom from a planar structure, via an intermediate environment between a trigonal bipyramid and a square pyramid, to a square pyramid. The magnetostructural correlation is explored in detail through the variation of the coordination environments by changing bond angles. The calculated results indicate that the magnetic coupling constant J is linearly related to bond angle theta, the spin populations rho on Cu atoms, and the square of the difference in energy of the unpaired electrons (epsilon(1) - epsilon(2))(2), respectively, when the bonding energy decreases with the variation of the coordination environments. However, the deviation from the linear relationship appears as the bonding energy increases. Another parameter, the difference of the squared spin populations on Cu atoms between the triplet and the broken states (rho(T)(2) - rho(BS)(2)), is found having an approximately linear relationship to J whether the bonding energy decreases or increases. So it may be more suitable than (epsilon(1) - epsilon(2))(2) in describing the linear relationship to J and extended to some other binuclear Cu(II) systems for the investigation of magnetostructural correlations.