This paper presents a two spin-orbit (SO) coupling parameter model of g factor for Ni2+-6X- clusters. Using this model, the g factors of NaCl:Ni2+ and NaBr:Ni2+ are calculated. The molecular orbitial coefficients are determined by means of a semiempirical method in calculation of the g factors. The results show that the contribution from the SO coupling of ligand ions to the g shifts can not be neglected for ligand ion possessing large SO coupling constant such as Br- or I-. This suggests that the calculation of g factor in some covalent crystals containing trasition metal ions should use the two SO coupling parameter model but not the classical crystal field model including only the contribution from the SO coupling of central transition metal ions.