Abstract: The photochemical processes of CBr₄-φ₂NH, CBr₄-LCV and CBr₄-LMG systems have been studied with the combination of ESR spectra and spin trapping technique. From the hyperfine structures of ESR spectra, and their variation varying with the concentration ratio of CBr₄ to φ₂NH or LCV or LMG, the free radicals such as (C₆H₅NHC₆H₅)₃ C, [(CH₃)₂NC₆H₅]₃C and [(CH₃)₂NC₆H₅]₂ C-C₆H₅ have been identified in these systems respectively in addition to Br.It could be shown that the partial charge-transfer complexes (CBr₄φ₂NH)^*, (CBr₄-LCV)^* and (CBr₄-LMG)^* have been formed with the UV absorption spectra of these systems. Therefore, it is concluded that the photochemical initial step of the above free radical photographic systems includes photolysis of both CBr₄ and (CBr₄-HX)^* (HX =φ₂NH, LCV, LMG).