SEM, EDX and XRD were applied to analyze SiC coatings deposited on the CVD furnace wall. The results show that the coatings consist of pure β-SiC in the lower-temperature block; however, there exist a few Si and α-SiC in the CVD SiC coatings within the higher-temperature block; the nucleation process and growth rate of SiC particles in the higher-temperature block are faster than that of the lower-temperature block; therefore, we can be sure that temperature is the main effect on the composition and microstructure of CVD SiC coatings.