Si1-yCyalloy has been deposited on SiC homoepitaxial layer acquired by chemical vapor deposition method on 6H-SiC substrates. X-ray diffraction, scanning electron microscopy, Ranman shift and other methods were applied to characterize the Si1-yCyalloy samples, and the crystal structure of Si1-yCyalloy is mainly focused on. The results are: The Si1-yCyalloy has good surface morphology and the XRD spectrum shows only a single characteristic diffraction peak ( 2θ≈28.5°), the crystal type is 4H;it′s roughly estimated that the carbon occupis about 3.7% of all. Raman spectrum shows as C/Si ratio increases, the partition of substitute C increases, and when C/Si increases to some extent, the unsubstitute C breaks the rythm structure of the alloy, and the quality of Si1-yCyalloy turns bad.