Equilibrium compositions of chemical vapor deposition progress for silicon carbide (CVD-SiC) coatings with MTS/H2 mixture system were calculated by means of HSC Chemistry5.0 code, and influences of the reaction temperature (T), the system pressure (P) and the composition of raw materials (molar ratio of H2 to SiCH3Cl3, β) were investigated. Thermodynamic analysis showed that the value of nC /nSiC in reaction product decreased to a minimum and then increased with the increase of the reaction temperature between 700-1600°C, which meant an optimal reaction temperature existed theoretically for CVD-SiC coatings with highest purity. Furthermore, CVD-SiC coatings with high purity were obtained by experiments under the reaction pressure of 10kPa, H2/SiCH3Cl3 value of 10 and reacton temperature of 1100°C, which was in accordance with the theoretical prediction.