C-N films were deposited on the 20CrMo alloy steel substrate by the Plasma Source Ion Implantation (PSII) method and TiN films were coated on the same material by the Physical Vapor Deposition (PVD) method. It was found that friction coefficient of C-N coating were relatively lower than TiN coating. And with the load increased, the friction coefficients of C-N coating and TiN coating were both decreased. Then the author puts forward the test rig, working under the conditions of 1,800 rpm, $20;N{cdot}m$ for 100 h. The observations by microscope showed the wear reduced. The antiwearing performance enhanced prominently. But the TiN coated gear had a more serious friction phenomenon than C-N coated gear. This is caused by that coating of TiN, which was made at a high temperature about $500^{circ}C$. The high temperature led to the substrate intenerated and the surface hardness had decreased from 850 HV to 630 HV. PSII method eliminates the tempering problem of the coating of C-N films, which had better wear resistance than TiN films. The friction and wear resistance of gears which coated by C-N films ameliorated significantly.