SiC conversion layer was fabricated by the chemical vapor reaction between graphite substrate and silica powder. The CVR process was carried out in nitrogen atmosphere at 175$0^{circ}C$ and 185$0^{circ}C$. From the reduction of silica powder with graphite substrate, the SiO vapor was created, infiltrated into the graphite substrate, then, the SiC conversion layer was formed from the vapor-solid reaction of SiO and graphite. In the XRD pattern of conversion layer, it was confirmed that 3C $eta$-SiC phase was created at 175$0^{circ}C$ and 185$0^{circ}C$. Also, in the back scattered image of cross-sectional conversion layer, it was found that the conversion layer was easily formed at 185$0^{circ}C$, the interface of graphite substrate and SiC layer was observed. It was though that the coke particle size and density of graphite substrate mainly affect the XRD pattern and microstructure of SiC conversion layer. In the oxidation test of 100$0^{circ}C$, the SiC converted graphites exhibited good oxidation resistance compared with the unconverted graphites.