Abstract: Q-Capon beamformer which based on the electromagnetic vector sensor array of quaternion field compared with the Capon beamformer in the traditional complex field has a better performance. However, this method has a bad performance in the case of the steering vector error and the polarization mismatch. What’s more, it may even cause a signal cancellation phenomenon. In this paper, interference and noise covariance matrix reconstruction method is promoted into the quaternion field. We use Q-Capon polarization-angle spectrum estimation to reconstruct the interference and noise covariance matrix because it can help us get the interference and noise power. The method proposed not only can effectively avoid the diagonal loading method for solving the diagonal loading factor, but also can overcome the bad performance caused by the pointing error and the polarization mismatch. The computer simulation shows that the method has a better performance compared with other methods in the quaternion domain.