The relative space position between aviation towed decoy and plane which is protected and release method of aviation towed decoy are the main factors that influence the result when missile is jammed by decoy. A new finite segment method was developed to make up the deficiencies of conventional finite segment method. Aerodynamic movement characteristics of aeronautic towed decoy were transformed to the question how to model and compute angles between tow and towing aircraft track coordinates. The geometry relationship between velocity vector of towing aircraft and tow was analyzed, so dynamic fallow models of tow and towing aircraft were established. The dynamic characteristics of towed decoy were calculated when towed aircraft does different flights. The result indicates that the arithmetic is simple, valid and better to simulate decoy-s dynamic characteristics.