The ta-C films with more than 80% sp3 fraction were deposited by FCVA technique, and then were bombarded by energetic N ion. The composition and structure of the ta-C films prior to and after the bombardment of energetic N ion is analyzed by x-ray photoelectron spectroscopy. The surface morphology is investigated by Atomic force microscopy .The result shows that the N concentration in the films slightly increase from 10% to 12% when N ion bombardment energy increases from 1000 eV to 2200 eV. The bombardment of energetic N ion induces the conversion of sp3 bond to sp2 bond. The CN bonds can be formed in the films after energetic N ion bombardment. Energetic N ion bombardment is implanted superficially. The RMS of the films decreases from 0.2 to 0.18 nm after the bombardment, and then increases again to 0.33 nm with the increment of the N ion energy. The friction test indicates that the minimum of friction coefficient is about 0.09 nm before ta-C film was bombarded by energetic N ion. The friction coefficient increased to about 0.16 nm after the bombardment of N ions. But the friction coefficient does not depend on the N ion energy.