Abstract: With the comprehensive application of digital drilling system in aircraft assembly, it is especially important to master the key technology of normal vector finding technology in digital drilling system. Based on three different digital drilling systems, the hardware selection, hardware layout, calculation model and workflow in the application of normal vector finding technology are introduced and compared and analyzed respectively. The key technologies of the digital drilling system include: in hardware selection, the measurement sensor with high accuracy and good reliability should be preferred; in layout, rectangular layout should be used as much as possible to ensure that the sensor ray normal intersects with the spindle axis; in presser foot size, the presser foot plane needs to be perpendicular to the spindle axis, and the presser should be made of softer material as much as possible to ensure that the area to be made is not crushed; in the calculation of the normal sensor, the presser foot plane should be perpendicular to the spindle axis. In the normal sensor calculation model, based on the robot drilling system, the least-squares model is used to solve with higher accuracy; based on the five-axis CNC machine tool drilling system, the binary angle model is used with higher accuracy.