Bis(2-benzimidazolyl)propane was synthesized by the reaction of o-phenylenediamine and glutaric acid which was accelerated by microwave irradiation and catalyzed by poly phosphoric acid(PPA) under solvent-free condition. By the method of orthogonal experiment optimize synthesis factors which affect the reation: o-Phenylent Diamine: glutaric acid:2.2∶1.0(mol:mol),PPA:9.0g,time of microwave irradiation:8min, and the power of microwave irradiation:160W. Under the optimal condition, the highest yield of Bis(2-benzimidazolyl) propane is 77.4%. The products were characterized by melting point determination, IR spectrogram,1HNMR spectra and 13CNMR spectra.