Methane, as a clean energy source, is one of the mainstays of global energy. Nevertheless, damage of moving parts operating in methane puts pressure on social security and economic development. Hydrogenated amorphous carbon (a-C:H) film is considered to protect the moving parts. Consequently, effects of structural modification originating from boron doping on interfacial evolution of a-C:H film under methane atmosphere were explored to reveal the lubricating factors of tribological system, and thereby improve the tribological performances of film applied in methane atmosphere. The key role, chemisorbed methane molecules, in interface sliding was revealed with experimental studies on interfacial evolutions of a-C:H and a-C:H:B films. The details about lubrication mechanism were explored with mathematical model and first principles calculation.