Abstract: A series of a-C:H films were deposited on silicon p(100) wafer and stainless steel substrates by DC reactive magnetron sputtering using graphite targets in an argon and methane atmosphere with different methane flow rate. Microstructures, mechanical and tribological properties were characterized systemically by FESEM, AFM, Raman spectroscopy, nano-indentation, CSM scratch tester and tribo-tester. The results showed that there was a lightly tendency of density of the a-C:H film with initially increase and then decrease as the increase of methane flow rate. The deposition rate of a-C:H film presented an increase as the increase of methane flow rate while the increase range was gradually reduced. Besides, the sp³ bond content, the nano-hardness and Young's modulus were increased at the initial stage and then decreased with the increase of methane flow. Frictional and wear behaviors showed that the a-C:H film deposited at the methane flow rate of 8 sccm was achieved low friction coefficient with 0.20 and high anti-wear with 6.48×10^-7mm³(N·m).