X ray CT system is used for nondestructive inspection in industrial field. There are some problems when we get the images of flat objects, namely rate of expansion and contrast. This study aims at solving these problems by contriving inclined X ray CT system. We improved Feldkamp algorithm, which is the conventional 3D reconstruction method and applied it to the data gained by inclined system. In order to evaluate the accuracy of reconstructed images quantitatively, the computer simulation using a Shepp-Logan phantom was implemented. Through the study the proposed method for the reconstruction of three-dimensional CT images was successfully implemented. Further improvement of image accuracy can still be done to get more clear and accurate CT images.