Aimed at the limitation of the ordinary methods of reverse engineering at present in unable showing the inner construction of pump parts, a new way on reverse engineering for impeller of pumps was presented. It utilized the multi-slice CT to scan its inner construction, and used a series of algorithms on digital image processing to treat the obtained images which contained information of design and inner construction of impeller on VC++ 6.0, 3-D model of surface was reconstructed and transformation from surface model to solid model was also fulfilled by pre-processing, 2-D image processing, 2-D geometric processing and 3-D reconstruction.