A dual layer silicon carbide (SiC) coating including inner porous SiC (rho-SiC) layer and outer dense SiC (d-SiC) layer was fabricated on the matrix graphite (MG) spheres of high-temperature gas-cooled reactor fuel elements by pack cementation and fluidized-bed chemical vapor deposition process to improve the oxidation-resistant property. Microstructure of the coating demonstrates different density and structure of the two SiC layers with no obvious boundaries between them. Weight gain curves of oxidation tests at 1773 K for 200 hours show that the coating could effectively protected the MG sphere by isolating the air infiltration with p-SiC layer as the main functional layer and d-SiC layer as the transition layer to improve the bond strength. Due to the transition function of p-SiC layer, the coated spheres could understand more than 50 times thermal shocking tests from 1773 K to room temperature with no stress cracking.