Based on complex body parts structure, the characteristics of batch processing and high accuracy requirement, in order to improve the efficiency of its alignment, put forward about the case accessories are the method of study the origin. During the study, in order to type boring and milling machining center for processing platform, build online detecting system for the body parts. By mathematical modeling and knowledge of analytic geometry, the rotary table any position of body parts in machining center is to find the origin, and determine the size of the work-piece origin of coordinates and the deflection angle. Checked by practice, this method is suitable for composite boring and milling machining center mass production of body parts in work, improve the efficiency of the box body parts processing precision and alignment.