Epitaxial 3C-SiC films have been deposited on Si(111) and Si(001) substrates via laser CVD with deposition rate of 12.32 and 15.56 m/h, respectively. The activation energy of 3C-SiC on Si(111) and Si(001) was 80 and 160 kJ/mol, and the root mean square (RMS) roughness (w) as a function of the film thickness (h) follows power laws of w similar to h(0.31) and w similar to h(0.06), respectively. The growth mechanisms of epitaxial 3C-SiC films on Si(111) and Si(001) was investigated based on the structural analysis and roughness evolution.