Abstract: Adaptive beamforming algorithm based on the linearly constrained minimum variance principle (LCMV) is widely applied in adaptive array processing. However, when LCMV is applied to the sub-array level, it causes the distortion of the mainlobe and heightening of the sidelobe. In order to solve these problems, an adaptive beamforming algorithm at sub-array level was proposed based on penalty function and eigen-space. In this proposed method, the penalty function was applied to control the adaptive pattern, meanwhile, interference was suppressed adaptively by setting constraints in interference subspace. Results show that, the proposed method can not only provide automatic suppression of jamming but also guarantee the adaptive pattern be close to the desired quiescent pattern, so that the mainlobe of the pattern is maintained and the level of the sidelobe is lowered. Furthermore, it provides better performance of output signal to interference plus noise ratio (SINR). Computer simulation results of array pattern and output SINR prove the validity of this proposed algorithm.