The crystal structure of the ytterbium hexameric cluster in CaF2 has been calculated in the framework of the embedded - cluster method within the shell model, in pair potential approximation. The crystal field parameters and scheme of the energy levels for Yb6F36 hexameric cluster were calculated in the exchange charges model. Also, the optical spectra of Yb3+ single center in CaF2 (cubic and tetragonal symmetry) was calculated and discussed.