The oxidation behavior and electrical resistivity of reaction-bonded silicon carbide (RB-SiC) at high temperature (900 °C) had been studied in this paper. The results showed that the weight of RB-SiC would be increased when it was oxidized at 900. The relationship between the weight-gain of RB-SiC and oxidation times followed the parabolic curve. The oxidation resistance of RB-SiC at 900 could increased by the increase of SiC particles sizes. But the electrical resistivity of RB-SiC had not affected by the oxidation at 900. The oxidation mechanism of RB-SiC and the affecting factor on oxidation of RB-SiC were analyzed and discussed.