Abstract: In this paper we propose a matrix weighted beamforming method which constrains the magnitude ripple range of the mainlobe. Compared with the methods available, our method can control the shape of the mainlobe, the sidelobe level and the null depth of beampattern more effectively. With the noise and systematic errors existed, the estimation of signal power is of better robustness. The covariance matrix of the weighting matrix can be obtained by the matrix weighted beamforming method, and the weighting matrix can be then secured by the eigen-decomposition of the covariance matrix. Meanwhile, the minimum scale of the weighting matrix dimension can be determined by the dominant eigenvalues. With the beampattern shape controlled, this method can maintain the performance of the signal power estimation and the system complexity can be efficiently reduced.