Abstract: The single oxide films damage at different laser energy values was studied with the photo-acoustic method. The acoustic acquisition was established. The frequency spectrum curves was obtained by the Fourier transform of in-time signals. In the experiment, we compared and analysed the frequency spectrum curves from 24 kHz to 40 kHz between the damaged film and undamaged one. By extracting frequency features and establishing frequency curve similarity function, it was possible to judge whether the optical film was damaged. The experimental result shows that the acoustic frequency method can be easily efficient to judge accurately film damage and it can be also used in online inspection conveniently.