SiC coating is prepared successfully on C/SiC ceramic matrix composites by the reaction method. The phase structure and components of the coating are investigated by XRD. The profile and surface micrograph are observed by SEM and optical metallography microscopy,and the forming course of SiC coating is analyzed. The result shows the main component of the coating is SiC and a little of Si. There is a good gradient structure and no obvious interface between the uncracked SiC coating and C/SiC substrate. On the contrary, if there were no gradient structure, the SiC coating would crack because of the great residual stress.The uncracked SiC coating prepared by the reaction method matched with CVD SiC coating excellently. At the same time,the CVD SiC coating fabricated on it has no dot defect.