Relaxed static stability, as an important technology in active control technology, has been widely popularized in the aviation industry. The application of this technology can not only greatly improve the maneuverability of the aircraft, but also bring considerable economic benefits to aircraft designers. However, with the relaxation of the aircraft's static stability margin, it will lose the stability of the aircraft, making it difficult to control, and also posing a new challenge to the design of flight control system. This paper takes the relaxation of the static stability technology's requirement on the deflection rate of the rudder surface as the research objective. Firstly, based on theoretical analysis, combined with rigorous formula derivation, a method for calculating the deflection rate demand value of the rudder surface was proposed, and then a certain aircraft model was taken as the research object, and different static stability margins were relaxed. Finally, the effect of relaxation of static stability on the demand of aircraft rudder surface deflection rate was analyzed through simulation verification.