Shell parts are widely used in aeroengine control accessories. A large number of small aperture threads are distributed on the surface of these parts. In the whole process of shell production and processing, thread processing is the core process that affects the processing efficiency and accuracy The existing thread processing technology is as follows: first, roughly milling the shell thread by using the NC machining center and then conducting manual tapping. This processing technology has the disadvantages of poor consistency, low processing efficiency, and many special fixtures. At the meantime, the phenomenon of positive cone is easy to appear when milling the thread. In view of these problems, this paper proposes and designs a special thread milling method for processing, which solves the programming problem caused by the shortening of the cutting edge through macro programming. Therefore, the thread can be processed together with the bottom hole, which reduces the manual tapping process and various threads with the same pitch and different specifications can be processed by one cutter. Finally, two batches of parts are verified bt experimental process, and the experimental results are analyzed to verify the reliability of the scheme of processing optimization.