Abstract: The calculated results by INDO method show that in the PrCl₃(OC₄H₈)₃ comlex the bond orders of Pr-Cl bond are decreased and the energies of the molecular orbitals corresponding to them are increased. The results imply a charge transfer from O to Pr caused by coordination, leading to decreasing the Pr-Cl bond energy,and the redu-ction of the charge difference between Pr and Cl would increase the covalent percen-tage of Pr-Cl bond.It is expected that the alkylation reaction may be then carried out favorably and the complex activation would be selective for Pr-Cl bond due to the for-mation of dipolymer.