Abstract: An analytic approximation wave function of free ion Ni~(2+) is obtained from Watson′s SCF-3d orbit. Crystal field energy levels in the ZnWO_4 : Ni~(2+) crystal are then calculated with this wave function using ligand theory. The calculation are based on real C_2 symmetry of the crystal and according to the descending symmetry devided in two steps. O_h C_(2v) and C_(2v) C_2. Sometimes it is difficult to determine the numerous parameters from spectral data in case of lower symmetry crystal. We try to overcome this difficulty. The theoretical calculations are in good agreement with the experimental results.