Graphite substrate is prone to corrosion and oxidation, which severely limits its application. Herein, silicon carbide (SiC) coating is synthesized on graphite substrate by chemical vapor deposition (CVD) to improve the oxidation and corrosion resistance. MTS, as carbon source and silicon source, was brought into the deposition chamber by bubbling H2, and H2 was also used as a diluent gas in the reaction process. The substrate position was 350 mm during the coating preparation process, the deposition pressure was 2 kPa, the deposition temperature was 1 100, 1 150, 1 200 and 1 250 ℃, respectively; the H2/MTS molar ratio was 10, 15, and 20, respectively; the MTS flow rate was 440 g/h, and the deposition time was 3 h. Combined with the thermodynamic analysis, some characterization methods including scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to the relationship between the temperature and the gas phase equilibrium composition at different H2/MTS molar ratios. Then, the effects of process parameters on the deposition rates and microstructures of the coatings were studied. Finally, the formation mechanism of the preferred orientation structure of the SiC coating was further discussed. The results show that the composition of gas-phase species in the deposition process of SiC coating were mainly CH4, SiHCl3 and SiCl4 at low temperature, while SiCl2 and C2H2 at high temperature, which verified that the pyrolysis of MTS firstly produced silicon-/carbon- chlorosilane compounds and alkane compounds, and then formed SiC film. The deposition rates of coatings increased rapidly with the increasing temperature, which were further controlled by the surface chemical reaction. Meanwhile, β-SiC tended to grow along the (111) crystal plane, forming the <111> preferred orientation when the activation energy of the reaction was 207.32 kJ/mol. With the increase of deposition temperature, the tendency of <111> growth direction of grains was gradually enhanced, resulting in enhanced the grain-like growth. Thus, the average grain sizes and the variability of the coatings increased, resulting in the increase of coating roughness. As the H2/MTS ratio increased, the deposition rate decreased due to the reduced MTS concentration. Then, the average grain sizes of the coatings and the variability of the grain sizes decreased, resulting in reduced surface roughness of the coatings. When the molar ratio of H2/MTS was small, the number of C active sites on the surface of the substrate increased due to insufficient H2, resulting in a decrease in the oxidation resistance of the coating. SEM showed that the surface of the coating exhibitted a dense and cauliflower-like morphology composed of gravel-like grains. This was due to the fact that the deposition process of the SiC coating was controlled by the surface chemical reaction. When the deposition temperature was low, and the gas-phase precursor molecules can continuously nucleate on the surface, while the adsorption molecules on the surface had poor migration ability, so cauliflower-like morphology grew in all directions. It is concluded that when the deposition temperature is 1 150 ℃ and the H2/MTS molar ratio is 15, CVD-SiC coatings with high purity and density, low surface roughness can be prepared at a rapid deposition rate.