Effects of the flow rate of C3H8 passed through hydrogen plasma on deposition rates and rnicrostructures of 3C-SiC films on Si (100) substrate were investigated by a reflection electron diffraction, an X-ray diffraction and an ellipsometric measurement. The deposition rate of the films increased independently of the flow rate of C3H8 with increasing the flow rate of SiH4. The films grown with increasing the flow rate of C3H8 kept single crystalline structure even at high flow rate of SiH4. Hydrogen radicals generated from C3H8 decomposition by plasma increase with increasing the flow rate of C3H8, and play important rolls to keep epitaxial growth.