The invention relates to a casting defect ray detection system which comprises a PLC, a casting transport vehicle, a detection chamber, an X-ray generator and a detection device, wherein the casting transport vehicle is used for transporting a casting into the detection chamber, the X-ray generator and the detection device are arranged in the detection chamber, the detection device comprises a detection platform body, a detection guide rail, a detection platform, a casting clamp and a casting drive structure, the casting transported by the casting transport vehicle is mounted on the detection platform by virtue of a casting clamp, the casting drive structure is used for driving the casting to transversely move and rotate, the X-ray generator generates X rays to realize detection of the casting, and the PLC is used for controlling the casting transport vehicle, the detection chamber, the X-ray generator and the detection device. According to the casting defect ray detection system, transportation, transmission and rotation of the casting are all controlled by adopting the PLC with PLC bus control as a center, and axial and radial detection of the casting is realized by virtue of the casting drive structure, so that the manual regulation time is saved, and the integral detection time of the casting is greatly increased.