Taking the structural features of Multi-Function Displays (MFDs) and the Head-Up Display (HUD) in the cockpit into consideration,we designed a Line of Sight (LOS) measurement system with simple structure,which was composed of a camera fixed on the helmet,a processor,and cockpit structural features.A new method was proposed which used the accurate structural features of MFDs and HUD together with Orthogonal Iterative (OI) algorithm to obtain the camera pose,which was then translated into LOS.A series of simulation experiments were made according to the cockpit structural features.The simulation results showed that:1) the system has a high measurement accuracy;and 2) the method based on cockpit structural features is rational and effective.