The sideslip angle of an aircraft is a highly significant state parameter. The commonly employed atmospheric sensors typically exhibit rather poor measurement accuracy for the sideslip angle in the air, especially when the aircraft undergoes large lateral maneuvers. The traditional Kalman filtering approach relies on precise modeling and aerodynamic parameters. If the model is inaccurate, deviations will occur in the estimation results. In this paper, on the basis of the traditional Extended Kalman Filter(EKF) algorithm, the accuracy coefficient of the aircraft's aerodynamic data is introduced as a state variable to establish an extended aircraft model, enabling it to participate in the iterative calculation of the Kalman filter along with other aircraft state quantities, aiming to provide the flight control system with robust online calibration capability of aerodynamic parameters and achieve precise estimation of the sideslip angle.