The eigen-projection matrix processing algorithm can be used to maintain the mainlobe pattern while suppressing sidelobe interference.However, the performance is significantly reduced in the situation that the power of the mainlobe interference is on the same level as the sidelobe jamming.In order to solve this problem, a new method is proposed by reconstructing the mainlobe interference eigenvector space.Different methods are used for calculating the eigenvectors corresponding to the strong and weak mainlobe interferences, which jointly construct the mainlobe interference eigenvector space.Then, the covariance matrix is pre-processed by the eigen-projection matrix, and the adaptive weight vector is calculated according to the MVDR criterion.Simulation result shows that: the algorithm effectively maintain the mainlobe pattern while suppressing sidelobe interference when there are both strong and weak mainlobe interferences.