Abstract: To solve the estimation problem of ionospheric delay corrections within satellite-based augmentation system(SBAS), an estimation method, which use the Kalman filter to estimate ionospheric delay of the navigation signals, is proposed. The ionospheric vertical delay and related change rate of the ionospheric grid points are estimated simultaneously. The system model is established on the basis of the slow-variant character and the measurement model is constructed on the basis of the grid model involved in the SBAS. The relevant analysis is conducted by the simulation method. The results indicate that comparing with the traditional ionospheric correcting method,this method can estimate the realtime ionospheric corrections with enough accuracy and can be an available for calculating the ionospheric differenced corrections in the SBAS.