The invention belongs to the field of machining of semiconductor materials and designs a method for cutting CdS single crystal. The method includes steps: using a flat grinder for grinding a growth face of a CdS crystal ingot; adopting an X-ray diffractometer for orientation of the ground end face; rounding the CdS crystal ingot, and manufacturing a main reference face and an auxiliary reference face; using a vacuum table for adsorption of the CdS crystal ingot, and placing the main reference face of the crystal ingot downwards; adjusting cutting parameters of an electric spark cutter to cut the crystal ingot; after cutting is finished, performing kerosene soaking, adopting hot ethyl alcohol for flushing cut crystal plates, putting a cutting clamp in hot water at 80 DEG C to make glue soft, and taking down the crystal plates to carry out the next operation. By means of non-contact spark cutting for cutting n-type CdS crystal ingots, cutting efficiency can be greatly improved, and fragments are reduced.