1. A multi-energy CT imaging system comprising: a stage for carrying an object to be inspected; a voltage-regulatable X-ray generation device for emitting X-rays for radiating said object to be inspected; a detector for receiving X-rays emitted from said X-ray generation device and penetrating said object to be inspected, and for outputting detection data; a rack having said X-ray generation device and said detector mounted thereon; and a data processing and control device for controlling said stage, said X-ray generation device, said detector and said rack, processing detected data from said detector, and during one rotation of scan of said X-ray generation device, evenly dividing a circular track of said X-ray generation device into angle intervals of a predetermined number according to a predetermined number of energies and setting a different high voltage of said X-ray generation device for each angle interval, and when said rack rotates from the current angle interval into a next angle interval, controlling said X-ray generation device according to an instruction from said data processing and control device to switch said X-ray generation device to a voltage set in the next angle interval.