1. A system for generating a CT slice image, comprising: an MIP image generation module for generating a sagittal MIP image and a coronal MIP image of a reconstructed three-dimensional image; a region of interest determination module for determining an image range in an original slice of the reconstructed three-dimensional image, and determining the parts of the sagittal MIP image and the coronal MIP image within the image range as a first region of interest and a second region of interest respectively; an angle setting module for rotating the first region of interest to a plurality of first specific angles for a plurality of times, and rotating the second region of interest to a plurality of second specific angles for a plurality of times; a curve determination module for generating a plurality of first two-dimensional projected curves of the first region of interest for the plurality of first specific angles, and generating a plurality of second two-dimensional projected curves of the second region of interest for the plurality of second specific angles, each first two-dimensional projected curve representing maximum CT values of columns of pixels of the first region of interest distributed along a longitudinal axis of an image on which the first region of interest resides, each second two-dimensional projected curve representing maximum CT values of columns of pixels of the second region of interest distributed along a longitudinal axis of an image on which the second region of interest resides; a match module for respectively selecting a first two-dimensional projected curve and a second two-dimensional projected curve matching with a part to be diagnosed based on features of the plurality of first two-dimensional projected curves and the plurality of second two-dimensional projected curves as a first matched curve and a second matched curve; and a slice generation module for determining a slice position range and a slice angle based on the features of the first matched curve and a first specific angle corresponding to the first matched curve and based on the features of the second matched curve and a second specific angle corresponding to the second matched curve, and generating a slice in the reconstructed three-dimensional image in accordance with the determined slice position range and the determined slice angle.