Abstract: In order to inspect large objects using short linear-detector array, several kinds of CT multi-scan modes have been developed, of which RT (rotation-translation) scan mode is practical in engineering. In this paper, we propose a backprojection-filtration(BPF)-based reconstruction algorithm for unilateral off-centered RT multi-scans. The proposed algorithm can reconstruct CT image directly, without data rebinning process which was introduced in the existing algorithms. Hence it is of high computational efficiency and image spatial resolution. In addition, the projection data required in the image reconstruction are nearly half reduced. As a consequence, the field-of-view is enlarged under the same times of rotation and translation. The validity of the proposed algorithm is verified by the real CT data.