Highlights •Binary elements (Si, Mo) co-doping DLC films were prepared on high-speed steel. •The adhesion of Si-MoDLC/substrate was influenced by Si content. •The stable transfer film was hard to form in methanol. •The wear mechanism of Si-MoDLC films was investigated in both air and methanol. Abstract To overcome the constraints posed by high internal stress and weak bonding forces, and achieve DLC films exhibiting exceptional tribological characteristics. Si and Mo co-doped DLC (Si-MoDLC) films were fabricated via the double-target co-sputtering technology. The results revealed that Si was mainly present in SiC and SiO forms, while Mo existed mostly in MoC and Mo forms. With an increase in Si content from 0 to 14.4 ± 0.2 at.%, the ratio of sp3/sp2 (peak area ratio) increase from 1.2 to 2.1. The hardness decreased first and then increased, while the adhesion increased first and then decreased. The Si-MoDLC film with 3.4 ± 0.2 at.% Si and 7.7 ± 0.2 at.% Mo exhibited the lowest hardness (13.4 GPa) and the highest adhesion (340 mN). The tribological properties of thin films were significantly affected by Si content and the testing environment. In the air, the Si-MoDLC film containing 14.4 ± 0.2 at.% Si displayed the lowest friction coefficient (0.07) and a low wear rate (1.1 × 10−7 mm3/N·m), while in a methanol environment, it showed the highest friction coefficient (0.21) and wear rate (14.6 × 10−7 mm3/N·m). These findings provide valuable insights into the microstructure and properties of Si-MoDLC films and offer guidance for the application of DLC films in alcoholic environments.