The effect of the geometrical parameters of the inner structure of the crucible on the sublimation growth of bulk SiC was investigated. It was found that the gap between the seed crystal and the guide-tube was the important parameter for the single crystal growth separated from polycrystal. The growth rate ratio of the single/poly crystal increased up to 4. The broadening angle of the single crystal was controlled in the range of 0-30degrees by changing the taper angle of the guide-tube. The crystal quality in the periphery was improved compared with the crystal grown without the guide-tube. The growth process was discussed considering the flux flow of the sublimation gas.