The manufacturing industry are facing the globe market competition in the 21st century, and lots of manufacturing companies require urgently the rapid R&D technique to adapt the market, the rapidness and innovation are the basic characteristics of the product development. RE (reverse engineering) technique,with its efficiency and rapidness, is becoming one of the key techniques for product research and development, RE(reverse engineering) system has been studied. Focused on the field of the rapid product development, the key technologies of reverse engineering system are studied in the dissertation.Firstly, the system structure of the product development based on reverse engineering is described and analyzed, the development and the research state of reverse engineering at home and aboard are summarized. Based on the analysis of the characteristics, problems and application fields of the existing digitizing method for reverse engineering, a new digitizing method for object based on liquid is presented. Comparing with the other methods, the digitized object is set up in the vessel with liquid. An intersection profile of liquid and the object would be appeared at the height of the liquid face, which is the section profile of the object in fact. The image could be captured and processed by the optical senor and computer system and the profile would be digitized. By changing the height of liquid face, the profiles of object could be obtained one by one. Then these data could be input the reverse CAD software, and the 3D model of the object could be reconstructed.Based on the principle of the new digitizing method for object based on liquid, the key technologies and problems are studied, the technique scheme are performed in the paper. These key technologies included the processing technologies of the liquid and object face, the scheme of capturing image, image processing and edge detection system, the calibration method and control system of equipment. According to analyzing wetting phenomena, the special liquid, which could be suit for image processing and low tension, is developed. An effective surface control equipment of liquid is designed and fabricated. The optical system is analyzed. The technique scheme of capturing image and image processing is designed and selected. The error recourses of the digitizing system are analyzed, the calibration method and algorithm are discussed, the software of control system, image processing, edge detection and interface to CAD are