The formulae of optical spectral energy levels and electron paramagnetic resonance (EPR) spectra of all configurations in trigonal symmetry of 3d2(3d8) ions are established on basis of strong field coupling mechanism by using the two-spin-orbit-coupling parameter model. Compared with the classical crystal-field approach which has only taken the spin-orbit coupling of the central transition-metal ions into account, the contribution of the spin-orbit coupling of the ligand ions to the optical and EPR spectra has been included in these formulae. When the optical and EPR spectra of the strong covalent crystals are calculated, reasonable results can be obtained if the two-spin-orbit-coupling parameter model has been put into action. As an application, the optical and EPR spectra of the NiX2(X=Cl,Br,I) crystals have been studied by the complete diagonalization method. The calculated results are in good agreement with experimental findings. From the investigation, a valid method to calculate the optical and EPR spectra of all configurations more accurately is provided.