Si thin film as planarizing layer were deposited on Reaction Bonded-SiC (RB-SiC) substrate by using RF magnetron sputtering technique. A set of orthogonal experiments were designed and performed to determine an optimized process condition by characterizing the evolution of the quality and surface morphology of the Si films deposited at various sputtering power, working pressure and Argon flow rate. The planarization was obtained at sputtering power of 120W, working pressure of 1.2 Pa and Argon flow rate of 40 sccm. Then smoothing of inductively coupled plasma (ICP) etching was performed and the surface reflectivity of samples processed under different treatment stages was investigated by using Lambda 950 spectrophotometer. The results show that the surface roughness Sq of RB-SiC sample under planarization and ICP etching process is reduced from 1.819 nm to 0.919 nm compared with untreated RB-SiC sample, and the surface reflectivity of the sample increased by 2%. Therefore the combinatorial optical polishing technology based planarization with RF magnetron sputtering and ICP etching process can enhance the performance of RB-SiC surface finishing.