A method and apparatus for reconstructing an incident energy spectrum for a detector are disclosed. In this method, an object to be inspected is illuminated with rays, and then rays transmitted through the object to be inspected are received by the detector to convert the received rays into data of a detected energy spectrum. The incident energy spectrum for the detector is reconstructed based on the data of the energy spectrum using a statistical iterative algorithm with a pre-established detector response function. With the above solution of the embodiments, the incident energy spectrum for the detector can be more accurately acquired, thereby reducing a distortion of the incident energy spectrum caused by the detector.