Hydrogenated amorphous carbon (a-C:H) film is considered to protect moving parts operating in natural gas, which is mainly composed of methane. Little knowledge on the key factors governing the tribological performances of a-C:H film in methane atmosphere limits application of film under natural gas. Load influences in the interfacial evolution of a-C:H film give information about above factors. Therefore, experimental and theoretical studies on load effects on frictional properties of a-C:H film under methane atmosphere were explored. It was found that frictional performances of a-C:H film were governed by the interfacial adsorbates and carbon dangling bonds, leading to reduced interfacial interaction with load. Furthermore, the structural influences in the frictional performances of a-C:H film under load were also discussed.