Reactive molecular dynamics simulations are employed to reveal the atomic-level mechanisms of tribochemical interaction-induced wear of H-terminated Si(110) in humid environment. The result shows that with interfacial water increasing, the surface wear first increases and then decreases under 2.5 GPa, while always decreases under 4.0 GPa. Four different Si atomic removal mechanisms are revealed, i.e., the stretching effect of interfacial bridge bonds, the weakening effect of H adsorption, the strain effect of O intrusion, and the pure shearing effect of a-SiO2 tip, and their occurrences show the same normal pressure and interfacial water amount dependence as the surface wear. The analysis on the prerequisite for their occurrences shows that the corresponding interfacial tribochemical interactions are first facilitated and then suppressed under 2.5 GPa, while suppressed under 4.0 GPa, which is the origin of the different normal pressure and interfacial water amount dependence of the surface wear. Moreover, it is found that a-SiO2 surface can provide H, O, or Si atoms to participate in the interfacial tribochemical interactions, and has an absolutely dominant role in the material removal of Si(110)-H compared with interfacial water, but its role is gradually suppressed by the increased interfacial water. This work sheds new and deeper lights on the mechanism for the effect of tribochemical interactions on the Si material removal in chemical mechanical polishing.