With the improvement of the digitalization of aircraft assembly and the wide application of new aerospace difficult-to-machine materials such as titanium alloys and composite materials, the traditional drilling process cannot meet the needs of processing. As a new type of hole processing technology, spiral milling hole technology shows many advantages over traditional drilling processing, especially difficult-to-machine materials such as titanium alloys and composite materials.It has been successfully applied in foreign aviation assembly sites, but strict technology has been adopted abroad blockade. At present, traditional end mills are mostly used for spiral milling in China, and there are many problems in the processing of end mills. Therefore, it is necessary to independently research the special tools for spiral milling holes suitable for aircraft assembly in China. Firstly, the movement characteristics of the tool during the spiral milling process are analyzed, and the mathematical description of the tool’s trajectory and cutting speed is established, and the problems existing in the spiral milling process of the traditional end mill are pointed out. Starting from solving the problems of the end mill, using the improvement of the group drill to the twist drill, based on the principle of free cutting and chip separation, a special tool for spiral milling holes with distributed multi-dot end cutting edges was designed. Use the trajectory equation to simulate the movement path of the cutting edge of the special tool and the end mill, and analyze the chip separation effect of the special tool; use the 3D modeling software to simulate the shape of the undeformed chip, and compare it with the end mill to the chip of the special tool Analysis of shape, cutting ratio of side edge and end edge. Through the spiral milling test of aluminum alloy, titanium alloy and composite materials, the chip separation, hole making effect and service life of the special tool were verified. At the same time, the cutting edge design of the special tool was analyzed in conjunction with the formation of the chip cap at the outlet of the titanium alloy hole. Inhibition of export glitches. Finally, starting from the selection of special tool geometric parameters, combined with the related experiments, analysis results and tool improvement process, the selection of the rake angle of the end cutting edge, the selection of the eccentricity and the center edge and the multi-lattice distribution of the end cutting edge are analyzed.