The application of CT can supply a new method of diagnosing beam independent of the beam model. By using this technology a precise two dimensions transverse-phase-space density(2D-TPSD) satisfying for a variety of applications could be obtained. This paper presents a code for the iteration rebuild algorithm (ART) of the method. As an example, the 2D-TPSD image by using this method was obtained. It is proved t hat this method could improve the measuring precision of the beam emittance that will provide a new checking for transport beam theories and beam dynamic theor ies.