In the process of countering the mainlobe interference by using the traditional blocking matrix, the interference signal is suppressed, but the complex envelope of the expected signal will also change, which will cause certain signal loss, affect the Signal-to-Noise Ratio (SNR) of the output, and is not conducive to subsequent signal processing.To solve this problem, the construction method of the traditional blocking matrix is improved, and a new algorithm based on the improved blocking matrix is proposed.The received signal is preprocessed by the improved blocking matrix, and then adaptive beamforming is performed.Simulation results show that, under the same conditions, this algorithm reduces signal loss, increases the Signal-to-Interference-plus-Noise Ratio (SINR) gain of the array output, and has better anti-interference performance compared with the traditional blocking matrix.