Geometrical optimization and theoretical calculation of the vibrational spectra have been performed for his(C-p-carboranyl) (C2B10H11)2 by using Gaussian 94 program at STO-3G and 6-31G basis sets respectively. The optimization bond lengths are in agreement with X-ray experimental values. The calculated results show that in the title compound two icosa-hedral carboranyl cages seem rigid and the D5d arrangement is more stable than the D5h ar-rangement. The assignments have been made on the basis of analysis of vibrational mode.The carboranyl cage can be regarded as a pseudoatom. Raman line at 250cm-1 correspounds to the quasidiatomic molecule vibration.