Two-photon polymerization initiated by a bimolecular initiating system composed of 7-diethylamino-3-(2 ' -benzimidazolyl)coumarin and diphenyliodonium hexafluorophosphate was investigated. The photosensitizer has been proven to possess large two-photon absorption cross-section for 800 nm femtosecond laser. The sensitizer/coinitiator system has high photosensitivity for the photopolymerization of methyl methacrylate. This photopolymer system has been demonstrated for fabricating three-dimensional microstructure.