By diagonalizing the complete energy matrix for d3 configuration ion in a trigonal ligand-field based on ligand-field theory，optical and EPR spectra of Cr3+：Be3Al2(SiO3)6 system are studied，the results of which are in good agreement with experimental facts. By analyzing optical and EPR spectra of (CrO6)9- cluster，the local polarization of oxygen ligands in (CrO6)9- cluster are studied. Results show that oxygen ligands in (CrO6)9- cluster exhibit remarkable polarization effect due to the effect of surrounding environment.