In order to obtain optimal processing parameters of UV-assisted SiC chemical mechanical polishing quickly, according to the theory of optimum polishing condition when chemical action and mechanical action are in equilibrium, the effects of pH value of polishing solution, the concentrate of hydrogen peroxide (H2O2), concentration of Fe2+ and UV power on the formation rate of oxidation film on the substrate surface (chemical action) are explored by electrochemical test method; Under the condition of maximum oxide film formation rate, the material removal rate (MRR) and surface roughness (Average roughness, Ra) were used as indicators to investigate the effect of process parameters on the oxide film removal rate (mechanical action) during the processing of SiC by adjusting the process parameters such as polishing pressure, polishing disc speed and polishing fluid flow rate, and to seek the balance point of mechanical and chemical action to obtain the optimal process parameters of SiC CMP under the action of UV light. The results reveal that the chemical action reached its maximum when the pH value is 3, the mass fraction of H2O2 is 4%, the concentration of Fe2+ is 0.4 mmol/L and the UV power is 32 W. Under the condition of maximum chemical action, chemical action and mechanical action are closest to the equilibrium point when the polishing pressure, polishing disc speed and polishing fluid are 38.68 kPa, 120 r/min, 90 mL/min respectively, at which the MRR of 92 nm/h and the lowest Ra of 0.158 nm can be obtained. Based on the results of the study, electrochemical testing can be used as an effective means to explore the processing parameters required for the faster rate of oxide film formation on the wafer surface and further adjust the process parameters to match the chemical action rate with the mechanical removal rate to efficiently obtain high material removal rates and surface quality.