Aeronautical thin-walled part is prone to cutting deformation because of poor rigidity and low manufacturability， which is one of the most difficult problems in mechanical machining. The aeronautical thin-walled part is studied on purpose of reducing the deformation. First of all, using the finite element analysis (FEA) method, the part deformation of cutting force was analyzed. And then, by anticipating the thinwalled part under the effect of cutting force of machining deformation and its corresponding springback amount, adopting the method of deformation of the active compensation, the cutting depth of the compensation of tools was revisied in the points of workpiece. By the calculation of finite element, the maximum error of the tool cutting points after compensation was reduced 95% lower with respect to compensation before. At the same time, the distribution of machining error of aeronautical thin-walled part was more uniform and fluctuation range of error value was even smaller. Then cutting and the real time monitoring system for monitoring the machining process was designed. A systematic method for improving the accuracy of cutting aeronautical thin-walled part is formed.