As a modern design method that contrary to traditional design, Reverse engineering (RE) plays an important role in accelerating conceptual design and physical design. The key problem of RE is how to obtain point data, process data and reconstruction data for a prototype. Therefore, this study focuses on the key steps of processing point cloud and reconstruction mode. Based on RE system of mechanical structural design, the dimensional surface module is established. The scattered point cloud data are acquired by optical scanning the physical object using three-dimensional coordinate measuring machine (CMM) and an optical scanning device. After the establishment of selected model, data process for prototype, includes noise elimination, data interpolation, data smoothing, data filtering, data splicing and surface reconstructing, are conducted subsequently. Through processing of measurement data, a CAD model is created and fabricated in stereo lithography apparatus (SLA) machine.