Through molecular dynamics simulations, the friction behavior between diamond-like carbon (DLC) films with different sp3 fractions and Si3N4 bulk was studied under various sliding velocities and loads. DLC films with moderate sp3 fractions demonstrated superior tribological properties, with lower frictional forces, smaller shear deformations and wear, and fewer sp3-sp2 transitions under equivalent sliding velocities and loads. Increasing sliding velocity promoted rapid mixing of the contacting interface, reducing shear deformations and adhesive wear. High loads disrupted DLC film surface structure, leading to a lubricating layer that shifted friction behavior from adhesive to abrasive wear, while suppressing sp3-sp2 transitions and releasing internal stress. These findings hold crucial implications for optimizing DLC film friction performance and applications.