The positions of the absorption lines in ruby are calculated with the general electrostatic interaction parameters in the ligand-field theory. Consistence of the theory with experiment is slightly better than those obtained previously. The effects of molecular orbi-tals on these parameters are discussed. Similar results are obtained by a calculation using two covalence parameters and other known free-ion parameters. In this method, the calculated values of Nπ≌0.92 and Nσ≌0.89 are obtained. The parameters in the generalized effective Spin-Hamiltonian are calculated. It is found that the g-factor in the modified term results from the contribution of the fourth order perturbation, and its order of magnitude is about 10-5. The effective Hamiltonian which is used to describe the R line of ruby was obtained.