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In order to investigate the nano-friction evolution characteristics of WC coating during the nano-scratching process, the molecular dynamics simulation model was established under different conditions (load, scratching-depth, scratching-velocity) by the large-scale atomic /molecular massively-parallel simulator. Results show that the friction force and coefficient of friction are increased with increasing the scratching depth. When the indenter scratches the specimen, the atoms are squeezed, sheared, and piled up in front of the indenter and at both sides of the groove along scratching direction. The instantaneous friction curve presents the distinct tribological characteristics during the initial and stable stages, and the dislocation, slip, interstitial, or vacancy occurs in the region under the indenter during the friction process. With increasing the scratching velocity, the strain energy of system exceeds the bonding energy caused by interatomic constraint. The atoms break the constraint and are stacked on both sides of the scratching grooves. Additionally, the surface morphology and the outer edge of accumulated atoms become rough, and defects appear in the subsurface crystal structure. This research provided the microscopic wear mechanism of WC coating at nano-scale during friction process.