Some improvements were put forward to modify the medical image reconstruction method based on MC algorithm. Computing redundancy, bad expansibility and “scalelike effect” lie in standard MC algorithm now. To solve the repeating calculation redundant problem, a suitable data structure was applied to seek cubes; by making segmentation result as the input of MC algorithm, the author eliminated the limitation of expansibility; by smoothing the normal vector of isosurfaces, this paper improved the image displaying effect. Finally, a special storage data structure was designed to save the non-manifold triangle model obtained from MC algorithm. The modification mentioned above has been realized in 3D reconstructing software-MedLG which was developed by authors’ institute and applied successfully in customized prostheses designing already. Moreover, The reconstructed model can also be used in biomechanics researching.