This study reveals the formation mechanism of the C/WO 3 low-adhesion sliding interface in WC/a-C films under low-humidity atmospheric conditions. Experiments show that sliding friction induces shear-stress-activated oxidation of WC nanoparticles, generating a WO 3 transfer film on the counterpart steel ball which chemically adheres via Fe-O-W bonds. This interfacial reconstruction establishes a stable C/WO 3 contact, achieving a low friction coefficient of 0.03. First-principles calculations confirm the selective transfer originates from the strong chemisorption of WO 3 on Fe (-24.94 eV), far exceeding the van der Waals interaction at the C/Fe interface (-7.23 eV), thereby stabilizing the WO 3 layer on the steel counterpart. Charge density and Bader charge analyses reveal significant electron transfer, directly supporting the Fe-O-W bonding mechanism for low friction.