In NC lathe cutting automatic programming system, in order to express and input part information effectively, to optimize CAPP data structure and to realize NC programming automation, the data structure of axial parts (including geometric information and processing information) was set up. Taking intersection algorithm to capture the key point information of graphic contour, the pixel feature extraction and input were realized when clients pick up the pixel needed, then data processing and storing were realized with the dynamic link library technology. Because different graphic pixel generated different types of lists, the graphic could be input and reappeared on the screen by opening database, then the data structure required by NC lathe cutting system could be output. The efficiency of the graphic input has been highly improved, it provides technology support for the NC lathe cutting visualization.