The invention relates to an energy spectrum CT imaging system, a data acquisition method of the energy spectrum CT imaging system and an energy spectrum CT image reconstruction method. The energy spectrum CT imaging system comprises a photon detector with multiple pixels. The data acquisition method of the energy spectrum CT imaging system can include the step that data acquisition is carried out on photons passing through an imaged object through the photon detector at multiple projection angles, wherein for each projection angle, the data acquisition method includes the step that data acquired from the photon detector is encoded according to multiple randomly-distributed pixel addresses.