Abstract: Most of the spatial spectrum estimation algorithms fail when the number of targets is lager than the array freedom. To deal with this problem, a spatial filtering method, which is based on steering vector transformation by using the method of interpolated array, is proposed in this paper. The entire observation space is divided into several sub-spaces, and the number of targets in each sub-space is guaranteed smaller than the array freedom by the priori information. By array interpolating, the steering vector of the entire observation is transformed into sub-space steering vector, which means the targets outside the subspace are inhibited. As the result, the mass targets DOA estimation issue in the entire observation space is transformed into a conventional DOA estimation issue in several sub-spaces. Simulative results show the effectiveness of the method presented.