Nowadays, as technology developing, traditional semiconductor material such as silicon (Si) could not satisfy the requirement of conditions in high frequency and high power environment. SiC (silicon carbide) has been recently applied in the semiconductor industry and optical components for its high hardness, excellent thermal conductivity, good chemical stability, wide band-gap, high critical electron mobility and so on. However for its hardness and chemical, mechanical stability, SiC is difficult to be processed. To overcome the difficulty in SiC polishing, the processing atmosphere is controlled by using the Bell-Jar type CMP apparatus which covers the entire elements of CMP with a pressure-resistant sealed chamber. The surrounding atmosphere, such as gas pressure and gas species may have a specific influence on CMP characteristics. The key for enhancing the SiC removal rate is regarded as the oxidation. To clarify the effect of oxidation, oxygen rich and lack of oxygen conditions are examined and the mechanism of SiC CMP is evaluated.