The automatic measuring system of stone milling force is studied in the article. The columned diamond milling cutters are used to mill stone on NC milling machines. Through analyzing the milling force, the mathematic model is established. Combining the measuring force index, the experimental facility of the automatic measuring system is established and solving methods of the key problems on the software data acquisition is detailed. The system is utilized to measure three component force of milling, that is, horizontal force, vertical force and axial force. Reliable data is acquired. Finally the automatic acquisition of data and the drawing of curve are realized. The achievement of automatic measurement of stone milling force provides theory basis for the further research on the wearing characteristics of diamond cutters, cutting quality of stones and the optimizing of processing technological parameter etc.