The on-line measurement technology of CNC machine tools is widely used in the on-line measurement of large-scale workpieces such as thin and composite materials, so as to ensure that the processing quality of the workpiece meets the requirements. Aiming at the problems of environmental interference and long time consuming in the calibration of on-line measurement system of CNC machine tools, according to the technical requirements in practical work, this paper proposes a calibration technology for on-line measurement system of CNC machine tools, which is suitable for the enterprise, and combines with compensation technology The correction of unit spacing is provided to ensure that the indication error of axis length meets the technical requirements. The experimental results show that the calibration method has good accuracy, high efficiency, and has the value of technology promotion.