The invention relates to an energy spectrum CT iterative imaging method and system based on an EBP. The method is used for re-establishing data under a plurality of energy spectrums acquired by a multi-energy-spectrum CT imaging system, such that a multi-energy-spectrum CT image is obtained. The method disclosed by the invention is capable of re-establishing the high-quality CT image without hardening artifacts according to multi-energy-spectrum CT scanning data; simultaneously, the method does not have geometric compatibility requirements to multi-energy-spectrum scanning data; in addition, the method is low in calculation amount and rapid in image re-establishing speed; the system is capable of scanning an imaged object; and thus, the multi-energy-spectrum CT scanning data and the high-quality CT image without hardening artifacts can be obtained.