A realistic dynamics simulation study is reported for the trans-cis photoisomerization of azobenzene triggered by the n→π~* excitation and the results show that the formation of cis isomer follows the rotational motion around the N=N bond.The simulation find that the CNN bond angle bending vibrations also play a significant role in the vibronic coupling between the HOMO and LUMO,which essentially leads a nonadiabatic transition of the molecule to the electronic ground state. A realistic dynamics simulation study is reported for the trans-cis photoisomerization of azobenzene triggered by the n → π ~ * excitation and the results show that the formation of cis isomer follows the rotational motion around the N = N bond. The simulation find that the CNN bond angle bending vibrations also play a significant role in the vibronic coupling between the HOMO and LUMO, which essentially leads a nonadiabatic transition of the molecule to the electronic ground state.