The shape-position tolerance of the joint surface of each component of aviation products is very high.  The traditional manual and semi-automatic processing methods have low efficiency and poor accuracy, and it is difficult to meet the task requirements. To improve the alignment accuracy of the tail cabin and the middle and outer wings of a large aircraft wing, this paper proposes a solution based on reverse engineering technology to combine automatic measurement technology with CNC machine tools for milling holes on the joint surface. According to the process requirements, the laser scanner is used to realize the method of contour size detection, reference extraction, milling amount calculation of large space parts, which is verified by experiments. The results show that the system significantly improves the assembly accuracy and efficiency of the tail cabin and the middle and outer wing, and has high application value and popularization significance. At the same time, it also has a positive role in promoting the digital design and processing technology research of other complex structural parts.