Abstract: In rough mountainous areas, beam-pointing mismatch problems always arise when a spaceborne Synthetic Aperture Radar (SAR) uses the traditional Digital BeamForming (DBF) approach in elevation to receive echoes, leading to the degradation of the receivers gain and system Signal-to-Noise Ratio (SNR). To solve this problem, an Adaptive Digital BeamForming (ADBF) approach based on the Capon spatial spectrum estimation is proposed. This approach first estimates the Angle Of Arrival (AOA) of the source signal in each range bin using the limited echo data. Then, it updates the weighting vector in the beamforming process, thereby enabling the receiving beams to precisely point to the signal source, and enhance the receivers gain and SNR. Simulation results suggest that the ADBF approach significantly improves the performance compared to the SCan-On-REceive (SCORE) approach, exhibiting robustness to system and source parameters variations.