Abstract: Based on the pole assignment, the influence of performance was analyzed and the principle on rapidity and stability was clarified with the methods of root locus and feedback. It is concluded that the positive lever effect obviously decreases the velocity of frequency of autopilot, which varies along with the open loop gain. Hence, a two-loop autopilot with a high gain can be designed without compensation network. Or it can enhance the stability. So it is a method that the accelerometer is fixed before the gravity to improve performance of autopilot. The simulation result shows that the conclusion is proper and important.