High cross-range resolution of forward-looking region is the key problem of radar imaging. This paper presents a multi-beam system to extend high resolution imaging domain based on the digital beamforming (DBF) technique. The Doppler bandwidth is increased in forward-looking direction while the symmetrical Doppler domain could be significant reduced. Then matched filter technique is employed to deal with the composed received echo. The feasibility and effectivity of this strategy were verified by simulation results.