With the fast development of computer software, 3D computer aided design (CAD) and computer aided manufacturing (CAM) are being improved rapidly and have been commonly used in industry, especially in medical area and moulding field. 3D CAD/ CAM has greatly shortened the mould development time, thus it plays an important role in product development and automatic production. It has been a serious topic about how to get the product design and also being manufactured in a short time to grasp the market opportunities in the competition of the developing manufacturing techniques, diversification and complexification of product demand. But not all the products have the design draft, for example, some of them were made by the mould of clay which came from craftsman by their hands. In order to conquer those problems, reverse engineering came into being. Reverse engineering could achieve a faster product design and manufacture, it also could be used in the field of vehicle components, home appliances, medical supplies (like human body measurement such as for artificial leg bones, tooth, etc.,), and rapid prototyping (such as precision casting products, industrial design, etc.). The so-called reverse engineering now targets to the existing mould (samples or manual model). It starts with the existing model, sampling surface data by data acquisition equipment (DAE) then acquire an ordered or unordered could of points. After that by the use of discrete geometry processing technology to get the CAD model of solid entity which computer could recognize. The following procedures of the CAD model could be redesigned or improved as required.