The present disclosure relates to a multi-spectrum X-ray grating-based imaging system and imaging method. The multi-spectrum X-ray grating-based imaging system according to the present disclosure comprises an incoherent X-ray source for emitting X-rays to irradiate an object to be detected, a grating module comprising a first absorption grating and a second absorption grating which are disposed in parallel to each other and are sequentially arranged in an X-ray propagation direction, and an energy-resolved detecting device for receiving the X-rays that have passed through the first absorption grating and the second absorption grating. One of the first absorption grating and the second absorption grating performs phase stepping actions within at least one period； during each phase stepping action, the incoherent X-ray source emits X-rays to irradiate the object to be detected； the energy-resolved detecting device receives the X-rays and performs spectrum identification of the X-rays； and after a series of phase stepping actions and data acquisitions over a period, at each pixel on the energy-resolved detecting device, X-ray intensities in each energy range are represented as an intensity curve.
