In the alignment of large parts of aircraft supported by numerical control localizer, the accurate orientation of large parts is the basis to ensure the accurate alignment of large parts. In order to reduce the error of the pose fitting of large parts, four key measurement points on large parts were measured by laser tracker. A method of fitting large parts pose vectors was proposed based on the position accuracy requirements of different measurement points. This method has the advantages of fast convergence speed and small fitting error, and is a good method to estimate the pose vector of  large components accurately.