In an effort to protect a RBSC (reaction-bonded silicon carbide) reaction tube, SiC films were chemically vapor deposited on RBSC substrates. SiC films were prepared to investigate the effect of the input gas ratios (dilute ratio, alpha = P-H2/P-MTS = Q(H2)/Q(MTS)) on the growth behavior using MTS (metyltrichlorosilane, CH3SiCl3) as a source in hydrogen atmosphere. The growth rate of SiC films increased and then decreased with the decrease of the input gas ratio at the deposition temperature of 1250 degreesC. The microstructure and preferred orientation of SiC films were changed with the input gas ratio; Granular type grain structure exhibited the preferred orientation of (111) plane in the high input gas ratio region (alpha = 3-10). Faceted columnar grain structure showed the preferred orientation of (220) plane at the low input gas ratios (alpha = 1-2). The growth behavior of CVD SiC films with the input gas ratio was correlated with the change of the deposition mechanism from surface kinetics to mass transfer.