Hydrogenated amorphous carbon (a-C:H) films were prepared by plasma enhanced chemical vapor deposition method with three different groups of processing parameters. After being radiated in oxygen plasma for 30min, the properties of all the a-C:H changed significantly. In order to investigate the oxygen plasma effect, Raman spectroscopy, Fourier-transform infrared spectroscopy, atomic force microscopy and ellipsometry were performed. From the above test results, it can be inferred that oxygen plasma radiation is a feasible method to change the nature of a-C:H films.