A study of the photoinitiated and thermally initiated cationic polymerizations of several epoxy systems with cyclopentadien-iron-biphenyl hexafluorophosphate ([Cp-Fe-biphenyl](+) PF6-) photoinitiator has been conducted. [Cp-Fe-biphenyl]+PF6-photointitiator is capable of photoinitiating the cationic polymerization of glycidyl ether and cycloaliphatic epoxides directly on radiation with long-wavelength UV light. Compared with the mono-arene iron complexes, the photoinitiating activity of [Cp-Fe-biphenyl] PF6 is higher than that of mono-arene iron complex I-261. When the photosensitizer benzoyl peroxide (BPO) is employed, [Cp-Fe-biphenyl]+PF6- is rendered much more efficient than diaryliodonium salt SR1012. The thermally initiated polymerization of epoxide / [Cp- Fe- biphenyl]+PF6- system was evaluated by DSC. It was found that the heat polymerization can occur in the systems of TDE85/[Cp- Fe- biphenyl]+PF6- without UV radiation at 71.6. However, the GCC/[Cp-Fe- biphenyl]+PF6- and ERL4221/[Cp-Fe-biphenyl]+PF6-systems are stable under 200.. The dark-cure of the system of epoxides/[Cp- Fe- biphenyl]+PF6- after UV radiation is obvious by DSC measure.