Abstract: Active free radicals in the photochemical hydrogen abstraction reaction between benzophenone and aromatic amines have been studied systematically by combination of spin trapping reagents and ESR.The results show that.(l) for primary and secondary amines,benzophenone abstracts H more efficiently from N than from α-C of amines to form N-centered radical (2) for tertiary amines, the abstraction of H is taken place on the α-C of amines to form C-centere dradical.