Taking asymmetric ice formation on wings caused to happen by troubles in single wing in deicing system as background, the stability in the aircraft's lateraldirectional system is studied. Firstly, a complex lateraldirectional model composed of dynamics model, actuator model, asymmetrically icing model, and the control law of stability augmentation is constructed. Secondly, by using the Monte Carlo algorithm, the calculation nodes are divided by sideslip angle β, roll velocityp, yaw velocityr. The stability points of each calculation node are obtained by dynamic simulation, and the stability regions near the stability points are obtained by the continuousadvancing algorithm proposed in this paper. and, the multiparameter coupled stability domain of aircraft's lateraldirectional system is constructed. Finally, the differences between stability regions in the case of noice and asymmetrical severe ice are analyzed. The results show that the asymmetric ice on wing may cause the deviation and contraction of the stability region in aircraft's lateraldirectional system, and the stability region contracts by under condition of asymmetric severe ice formation. Therefore, the aircraft deviates from predetermined trajectory under condition of asymmetric ice formation on wing, pilot must avoid rough operation surface, or aircraft will easily cross the stability region to induce flight accidents.