Abstract: When both mainlobe and sidelobe barrage jamming exist, the traditional four-channel mainlobe jamming suppression technique is no longer applicable for monopulse angle measurement. To tackle this problem, an adaptive monopulse angle measurement algorithm is proposed based on eigen-projection matrix preprocessing. Firstly, the eigen-projection matrix preprocessing is used to filter the mainlobe jamming in the sampling signal. Then, to suppress the sidelobe jamming in the echo signals, the adaptive beamforming with constraint is calculated by using the preprocessed sampling signals. Moreover, a four-channel monopulse system is formed. Finally, the monopulse angle measurement technique based on four-channel mainlobe jamming suppression is applied to the signals in the four channels. Simulation results show that the proposed algorithm can achieve good performance in angle estimation when both the mainlobe jamming and multiple sidelobe jamming exist at the same time.