We report a study on photo-ionization of benzene and aniline with incidental subsequent dissociation by the customized reflection time-of-flight mass spectrometer utilizing a deep ultraviolet 177.3 nm laser. Highly efficient ionization of benzene is observed with a weak C$ _4 $H$ _3 $$ ^+ $ fragment formed by undergoing disproportional C$ - $C bond dissociation. In comparison, a major C$ _5 $H$ _6 $$ ^{+\cdot} $ fragment and a minor C$ _6 $H$ _6 $$ ^{+\cdot} $ radical are produced in the ionization of aniline pertaining to the removal of CNH$ ^\cdot $ and NH$ ^\cdot $ radicals, respectively. First-principles calculation is employed to reveal the photo-dissociation pathways of these two molecules having a structural difference of just an amino group. It is demonstrated that hydrogen atom transfer plays an important role in the cleavage of C$ - $C or C$ - $N bonds in benzene and aniline ions. This study is helpful to understand the underlying mechanisms of chemical bond fracture of benzene ring and related aromatic molecules.