Based on the crystal field theory (CF mechanism) and the charge transfer mechanism (CT mechanism), the spin Hamilonian parameters (EPR parameters), the optical absorption spectrum and the charge transfer transition energy levels of C3H7NO2∶VO2+ crystal are calculated by the double spin orbit coupling parameter model, the high-order perturbation formulas of spin Hamiltonian parameters and the crystal field energy formulas. The results calculated by using the CF mechanism and the results calculated by using the double mechanism are compared. It is found that the contribution of the CT mechanism to the C3H7NO2 crystal doped with high valence vanadium ion (V4+) could not be ignored, when calculating EPR parameters of this crystal.