In this paper, we have synthesized a water-oil amphiphilic photoinitiator triethylene glycol benzoylformate (TGBF) based on benzoylformic acid and triethylene glycol, and investigated its UV-visible light absorption properties, photolysis mechanism, water solubility and ability to initiate photopolymerization by using UV-vis absorption spectrometer, electron spin resonance spectrometer and real-time infrared spectrometer. The research results show that TGBF has low molar extinction coefficients at above 300 nm, but it is able to undergo intramolecular or intermolecular hydrogen abstraction reaction to produce alkyl radicals to initiate polymerization of acrylate monomers under the irradiation of 405 nm LED. TGBF has good water solubility, and can effectively initiate polymerization of oil-based tripropylene glycol diacrylate (TPGDA) and water-based polyethylene glycol 400 diacrylate (PEG(400)DA). The final double bond conversions reach more than 80%.More importantly, TGBF has excellent ability to initiate deep polymerization of oil-based monomer TPGDA and aqueous monomer PEG(400)DA, with polymerization depths of 5.6 cm and 6.5 cm, respectively, demonstrating that it has a great potential in the field of deep-layer LED photopolymerization.