In order to address the performance degradation when coherent sources, array perturbations and finite-sampling exist, a robust adaptive beamforming using Iterative Adaptive Approach(IAA)-based interference-plus-noise covariance matrix reconstruction is proposed. Firstly, the method uses the IAA to estimate the accurate power spectrum, and further reconstructs the interference-plus-noise covariance matrix with the power estimated. The method reduces the integral region to the three-dimensional domain to reduce the influence of noise, which improves the reconstruction precision of the interference-plus- noise covariance matrix. Finally, the proposed method suppresses the interference signal by beamforming. Since IAA does not rely on the non-coherent assumptions of the signal, it could estimate the high accuracy of DOA and power when the coherent interference exists. Computer simulations show that, compared with other beamforming methods, the output Signal to Interference plus Noise Ratio(SINR) can achieve the optimal output under coherent interference, array perturbations and finite-sampling situation.