Reverse engineering is applied to design sophisticated forms such as car body. In the design process of reverse engineering, a clay model is created to express the designer's idea and to evaluate the designed shape, after which a CAD model is constructed from the measurement data of the clay model. Modeling a shape in clay takes considerable time and costs, so there are strong demands for a more efficient process. In this study, a design support system which enables designers to model shapes in virtual clay in virtual space was developed. Since the process is carried out using digital data, the time and costs for the modeling are drastically reduced. In the modeling process, virtual clay is cut and deformed using digital tools with aesthetic curves which can be easily and intuitively defined by the designer. In order to define aesthetic curves, two methods are proposed; one by using the deflection curves of a plate spring with minimum strain energy and the other by using constant rhythm curves with constant curvature changing rate. Modeling tests were also carried out to verify the validity of the developed system.