As well known the vibrational motion is a truly molecular property.When internuclear distances vary, followed the change of electron distribution and ionization potential, there arise a rather puzzling condition and that it is important to understand its influence on strong-field ionization.The availability of vibrational degree of freedom of molecules leads to a larger number of possible effects accompanying the tunneling ionization of molecules compared to the tunneling ionization of atoms.It is found out excited vibration plays a certain role in ionization that is drawn attention and studied by a few researchers.