Abstract: The main lobe interference will cause the main lobe distortion， peak offset and sidelobe level rise of the traditional adaptive beamforming algorithm， which will seriously deteriorate the anti-jamming performance of phased array system. In addition， when there is a desired signal in the received snapshot， adaptive beamforming will generate a null in the direction of the desired signal and reduce the gain of the received desired signal. To solve these problems， a main lobe interference suppression method based on eigenvalue oblique projection is proposed in this paper. Firstly， the eigenvalue oblique projection preprocessing matrix was constructed to filter the main lobe interference， then the influence of covariance matrix mismatch was reduced by diagonal loading. The proposed algorithm can effectively suppress the main lobe interference and the influence of the desired signal in the received signal. Simulation results demonstrate the effectiveness and robustness of the proposed algorithm for main lobe interference suppression.