In the present study, we obtained a-C:H films with different nanostructures by annealing from room temperature to 400 °C. The influence of the nanostructures on tribological performance in dry air and methanol environments was investigated by a reciprocating tribometer. Our results show that the tribological performance of a-C:H films follows different rules in the two environments. In dry air, tribological properties are controlled by the transfer film and mechanical properties. In methanol, friction and wear are determined by the hydrogen bonding structure, where friction coefficients relate on saturation effects of sp³-CH, and the wear properties depend on the “collapse effect” that the more the sp³-CH₃ and sp³-CH₂, the easier the wear out of bulk a-C:H films. Our work provides guidance for the application of a-C:H films in the methanol environment.