Frequency Diverse Array Multiple-Input and Multiple-Output(FDA-MIMO) has drawn a remarkable amount of attention due to its particular range-dependent beampattern. Firstly, the echo model of the FDA-MIMO radar is established; then the conventional Eigensapce-Based(ESB) beamformer is extended to this model. Finally, an improved ESB beamforming algorithm is proposed to enhance the performance in low Signal Noise Ratio(SNR). Simulation results show that the range-dependent interference from main lobe can be suppressed and the effectiveness of the proposed algorithm is verified.