In this paper, the electronic structures and energy levels of the complex ion (CrO4) as Cr-O distance changes are analyzed with the spin-polarized MS-Xα method, Under the symmetry Td the one-electron energy levels and eignfunctions, electronic configuration of ground state, optical transitions of lower excited state,and schematic diagram of the energy levels of the three complex ions,(CrO4)6-,(CrO4)5- and (CrO4)4-, are given, When the distance of ligands from the central ion is sma. ller than 2?(R≤2?), the results given by crystal field theory is not satisfactory. In this case, the influence of the distance of ligands from the central ion and the influence of the 4s or 4p atomic orbits in the central ion(transition metal ions to be considered must be taken into aceount.