Abstract: Aiming at the problem of monitoring the cutting state in the milling process of high-grade NC machine tools, the fusion of extra speedometer mounted on the spindle box is studied, and a method for estimating the cutting force and vibration of the milling cutter was proposed. Firstly, the frequency response function between the spindle front end and the accelerometer position was determined by impact modal test. Then, the dynamics of the spindle structure and its response coupling related to rotational speed and preload are analyzed. Finally, the signal transmission distortion from the tool to the accelerometer was compensated with a Kalman filter, and the improved tip displacement and force estimates were obtained using the weighted average data fusion method. The effectiveness of the proposed method was verified in the low speed and high speed five-axis CNC 7075 aviation aluminum alloy milling. The results show that this method can effectively improve the accuracy and robustness of cutting state monitoring, and the error of the estimation of cutting force and displacement is less than 9%.