Abstract: The orthogonal block matrix is needed in the generalized sidelobe canceller algorithm to offset the received signal and the desired signal. But there is a limitation on constructing the orthogonal block matrix in the actual pattern synthesis processing. In this paper, an improved sidelobe cancellation algorithm is proposed. The wavelet filter bank is used to block the desired signal component in received signals of antenna array for adaptive beamforming. The covariance matrix of array signal does not contain the desired signal component in the improved algorithm. So the desired signal cancellation problem in adaptive beamforming with the system error can be overcome. Also the proposed algorithm solves the problem that the generalized sidelobe canceller (GSC) beamforming algorithm needs to construct the blocking matrix which is orthogonal with the desired signal, thus the robust performance of the system is achieved. The effectiveness of the improved algorithm is verified by the simulation results. The simulation results show that the performance of the improved algorithm is better than the traditional minimum variance distortionless response (MVDR) method and the diagonal loading method based on MVDR algorithm.