Abstract: The design method of medical elastic assistive devicesbased on reverse engineering is proposed, and the expressionfor calculatingstrain energy of the elastic device is deduced in the paper. To increase designefficiency, the techniques of mesh simplification and parameterization areused respectively for decreasing scanned data and changing three dimensional data intotwo dimensional one. To provide doctors and sufferers with scientific foundation for choose of medical device, the relationship between the devicedimension and the strain energy is constructed by using the density function ofstrain energy.