Abstract: The differences between reverse engineering (RE) and traditional obverse design were compared, and the coordinate data collecting and modelling in RE were discussed.Taking tobacco rod forming parts as an example, the realization of RE in irregular parts CAD/CAM system was discussed, including application environment of software and hardware, data collecting, data processing, curved surface fitting and entity constituting.RE provides a new technology for designing and manufacturing tobacco machine parts with guaranteed design veracity, shorter developing period and higher rate of success.