The numerical simulation and in-situ X-ray topography were applied to observe the phenomena inside a crucible. Numerical simulation pointed out that macroscopic grown crystal quality such as grown crystal shape strongly depends on the temperature distribution inside a crucible. In-situ X-ray topography revealed that when the defects were generated, and how the defects were propagated. Most of defects were generated at the initial growth stage. It is important to control the initial stage in order to obtain a high quality SiC single crystal. Numerical simulation also suggested that it is important reduce the residual stress in a grown crystal in order to avoid the dislocation occurrence. From these results based on numerical simulation and experiment, SiC sublimation growth was controlled actively, and the large and high quality SiC single crystal have been grown.