Abstract: In this paper, according to the characteristics of the structure of right-angle milling head through the installation of right-angle milling head and the tip point compensation algorithm research, such as reference point by the cutting tool offset compensation method, controllers, two-way blade length compensation method, break through the narrow space of the complex structure is easy to appear when processing spindle interference and movement axis overtravel common bottlenecks; At the same time, the principle, error analysis and datum conversion of precision assisted off-line machining technology are discussed in detail to solve the coordinate system conversion problem of precision assisted off-line machining. The problem of narrow space combination machining of thin-walled shell structure is solved, which lays a good foundation for promoting the further improvement of spacecraft manufacturing level in China.