Abstract: A systematic review of the phase error of the conventional airborne InSAR data processing method is firstly presented, which is caused by the center-beam approximation, and the unknown terrain, and its effects on imaging quality and height accuracy are analyzed as well. Then, a novel airborne InSAR data processing method based on the BP algorithm and the time-varying baseline is proposed for addressing the center-beam approximation problem and reducing the height error due to the unknown terrain which have been both accomplished. Finally, the validity of the proposed method is testified by the simulation experiments.