Photon Counting Detector(PCD)is a device used to detect X-ray photons,which can directly convert the energy of photons into electrical signals to achieve photon counting and measurement.PCD-based energy spectrum computed tomography(PCD-CT)technology can provide additional energy spectral imaging information,and improve imaging quality while reducing radiation dose.Compared with energy integrating detectors(EID),PCD has advantages of high energy conversion efficiency,good imaging quality,exquisite structural design,and wide application range.It has broad application prospects in ultra-low-dose CT,specific disease diagnosis,and industrial inspection.The application of PCD-CT in spectral CT imaging was reviewed to provide a useful reference for its application in clinical medical diagnosis and industrial applications.