A correlation study between substrate and epitaxial wafer of 4H-N Silicon Carbide (SiC) is conducted on five aspects for the first time: thickness and doping concentration uniformity distribution, topography change, surface roughness and crystalline quality. The 4H-N SiC homoepitaxial layer is deposited on the commercial substrates from different manufacturers using the method of Chemical Vapor Deposition (CVD). These data are characterized using these methods of mercury-probe CV measurement, Fourier transform infrared reflectance, atomic force microscope, Flatness Measuring Instrument and X-ray diffraction. It is concluded that the resistivity distribution of SiC substrate has a direct impact on the growth facet of crystal, but has no obvious influence on thickness and doping concentration distribution of epilayer. In the meantime, the relationship between crystalline quality of substrate and epilayer is found. Based on this research, it is necessary that the discuss correlation between defects of substrate and epitaxial wafer.