The processing of cemented carbide workpieces during surface treatment poses significant challenges due to their exceptional hardness and wear resistance. The action mechanisms of Fenton’s reagent on cemented carbide during shear thickening polishing under varying pH conditions were investigated. Polishing experiments were conducted at pH values of 1, 2, 4, 6, 8, and 10, with pH 1, 6, and 10 selected for further analysis. Results indicated that the material removal rate peaked at 1353.2   nm/min, while surface roughness (Sa) minimized to 6.6   nm with shear thickening polishing slurry at pH 1. Electrochemical tests showed that the polarization current of Fenton’s reagent at pH 1 reached as high as 485 μA. X-ray photoelectron spectroscopy, energy dispersive spectroscopy, and nanoindentation tests revealed that the preferential dissolution of cobalt weakened the structural support for tungsten carbide (WC), reducing hardness from 24.0   GPa to 12.6   GPa and Young's modulus from 679.0   GPa to 442.7   GPa. Nanoscratch tests exhibited high coefficient of frictions at pH 6 and 10. Analysis elucidated distinct removal mechanisms: at pH 1, chemical corrosion and mechanical removal synergize for efficient material removal, creating a relatively shallow WC skeleton layer with incomplete cobalt dissolution. As pH increases, the chemical corrosion rate is relatively stronger than the mechanical removal, leading to a deeper WC skeleton layer, with the cobalt content increasing with depth. It was further improved that the polishing efficiency for cemented carbide during chemical enhanced shear thickening polishing, and provides a new solution for the surface treatment of cemented carbide.