The invention discloses a CT (computed tomography) system and a CT image reconstruction method. The CT system which comprises a ray source, a ray detector, a data collecting and processing unit, a main controller, a camera group, a tag group and a tag group processing unit, wherein the tag group is fixed on the surface of a detected object the camera group is used for acquiring the projection of the tag group on the camera group and the tag group processing unit obtains the initial position of the tag group and the position information after rotation according to the projection, and calculates to obtain the rotation matrix and displacement amount of the detected object. The CT image reconstruction method comprises the following steps: the tag group is fixed on the surface of the detected object to obtain the initial position of the tag group the position information of the tag group after rotating can be obtained after the detected object is rotated then the rotation matrix and displacement amount of the detected object can be obtained and then the CT image is reconstructed according to the rotation matrix and displacement amount. The requirement on the mechanical control accuracy is not high by adopting the CT system and the CT image reconstruction method provided by the utility model.
