In this paper, to overcome the signaltointerferenceplusnoise ratio (SINR) performance degradation in the presence of large steering vector (SV) mismatches between beam pointing and actual steering vector, we propose a robust adaptive digital beamforming (ADBF) algorithm.The approach iteratively estimates the mismatch errors of actual steering vector based on main lobe width to calculate ADBF weight.Simulation results show that the proposed approach can accurately evaluate the steering vector and avoid the loss of output SINR caused by steering vector mismatch in ADBF.