X ray CT is a vital technology for inspecting the internal structure of some objects. Various computing method models have been used to CT reconstruction. When image of the scanned object is recorded by the detector unit of finite area, the strip-based projection model is more suitable. In this paper, a simultaneous algebraic reconstruction technique (SART) for strip-based parallel beam projection model have been adopted. Furthermore, in order to reduce the radiation dose and avoid the blurring effect resulting from changes in physical and chemical properties of specimens during scanning, it is necessary to reduce the number of step-scanning. This algorithm combined with cubic spline interpolation can reconstruct high quality CT images in a small amount of data projection in numerical simulation.