A detection device for a CT system comprising: a low-energy detector assembly having a thickness in a thickness direction, and comprising surface-array low-energy detectors distributed on a circular cylindrical surface; and a high-energy detector assembly disposed under the low-energy detector assembly, in the thickness direction, the high-energy detector assembly comprises: a plurality of rows of high-energy detectors arranged at predetermined intervals, and the low-energy detector assembly comprising: first low-energy detectors which coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction and second low-energy detectors which do not coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction, characterized in that the plurality of rows of high-energy detectors are arranged in an axial direction of the circular cylindrical surface, and each of the predetermined intervals comprises a region without high energy detectors which is located between two adjacent rows of high-energy detectors of the plurality of rows of high-energy detectors in the axial direction. a low-energy detector assembly having a thickness in a thickness direction, and comprising surface-array low-energy detectors distributed on a circular cylindrical surface; and a high-energy detector assembly disposed under the low-energy detector assembly, in the thickness direction, the high-energy detector assembly comprises: a plurality of rows of high-energy detectors arranged at predetermined intervals, and the low-energy detector assembly comprising: first low-energy detectors which coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction and second low-energy detectors which do not coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction, characterized in that the plurality of rows of high-energy detectors are arranged in an axial direction of the circular cylindrical surface, and each of the predetermined intervals comprises a region without high energy detectors which is located between two adjacent rows of high-energy detectors of the plurality of rows of high-energy detectors in the axial direction. a plurality of rows of high-energy detectors arranged at predetermined intervals, and the low-energy detector assembly comprising: first low-energy detectors which coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction and second low-energy detectors which do not coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction, characterized in that the plurality of rows of high-energy detectors are arranged in an axial direction of the circular cylindrical surface, and each of the predetermined intervals comprises a region without high energy detectors which is located between two adjacent rows of high-energy detectors of the plurality of rows of high-energy detectors in the axial direction. first low-energy detectors which coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction and second low-energy detectors which do not coincide with the plurality of rows of high-energy detectors of the high-energy detector assembly when viewed in the thickness direction, characterized in that the plurality of rows of high-energy detectors are arranged in an axial direction of the circular cylindrical surface, and each of the predetermined intervals comprises a region without high energy detectors which is located between two adjacent rows of high-energy detectors of the plurality of rows of high-energy detectors in the axial direction.