An x-ray imaging system for performing an x-ray scattering imaging of an object, said system comprising an x-ray source, first and second absorbing gratings G1 and G2, an x-ray detector, which are orderly located on a propagation direction of the x-rays; wherein the system further comprises: a data processor unit for processing data information; and a controller configured to control operations of said x-ray source, first and second absorbing gratings G1 and G2, x-ray detector and data processor unit, so as to carry out the following process: the x-ray source emits x-rays to the examined object; one of the two absorbing gratings G1 and G2 performs phase stepping motion within at least one of their respective cycles; in each phase stepping step, said detector receives the x-ray and converts it into an electric signal; wherein through the phase stepping of at least one cycle, the x-ray intensity at each pixel point on the detector is represented as an intensity curve; the intensity curve at each pixel point on the detector is compared to an intensity curve when without the presence of the examined object, to acquire a variation in the contrast ratio of the intensity curves; a second moment of scattering angle distribution for each pixel on the detector is calculated from the intensity curve variation; and pixel values of the image of the examined object are obtained from said second moment of scattering angle distribution, whereby the image of the examined object is reconstructed. a data processor unit for processing data information; and a controller configured to control operations of said x-ray source, first and second absorbing gratings G1 and G2, x-ray detector and data processor unit, so as to carry out the following process: the x-ray source emits x-rays to the examined object; one of the two absorbing gratings G1 and G2 performs phase stepping motion within at least one of their respective cycles; in each phase stepping step, said detector receives the x-ray and converts it into an electric signal; wherein through the phase stepping of at least one cycle, the x-ray intensity at each pixel point on the detector is represented as an intensity curve; the intensity curve at each pixel point on the detector is compared to an intensity curve when without the presence of the examined object, to acquire a variation in the contrast ratio of the intensity curves; a second moment of scattering angle distribution for each pixel on the detector is calculated from the intensity curve variation; and pixel values of the image of the examined object are obtained from said second moment of scattering angle distribution, whereby the image of the examined object is reconstructed. the x-ray source emits x-rays to the examined object; one of the two absorbing gratings G1 and G2 performs phase stepping motion within at least one of their respective cycles; in each phase stepping step, said detector receives the x-ray and converts it into an electric signal; wherein through the phase stepping of at least one cycle, the x-ray intensity at each pixel point on the detector is represented as an intensity curve; the intensity curve at each pixel point on the detector is compared to an intensity curve when without the presence of the examined object, to acquire a variation in the contrast ratio of the intensity curves; a second moment of scattering angle distribution for each pixel on the detector is calculated from the intensity curve variation; and pixel values of the image of the examined object are obtained from said second moment of scattering angle distribution, whereby the image of the examined object is reconstructed.