The invention is applicable to the technical field of CT medical imaging, and provides a data processing method and a data processing device for CT scanning. The method comprises the following steps: performing CT scanning on a scanned object to get N projection images, wherein N is an integer greater than 1; performing CT reconstruction through an iteration method based on the N projection images, and correcting an intermediate image f for each iteration; and outputting a CT reconstruction image after iteration of the CT reconstruction is terminated. According to the invention, CT reconstruction is implemented through an iteration method, and the gradient images of the intermediate image are trained during each iteration, so that noise in the CT projection images is removed effectively, and useful information in the CT projection images is enhanced. Therefore, CT projection data needing to be acquired is reduced, the CT scanning time is shortened, the motion artifact of the scanned object is reduced, and the radiation dose is reduced.