One limitation of the single-stage acousto-optic tunable filter (AOTF) as a bandpass filter is the presence of large sidelobes higher than -9 dB. Multi-stage AOTF for suppressing sidelobes further is studied in this paper. The filter characteristics of single and multi-stage AOTF have been analyzed and compared theoretically and experimentally,and the advantages of multi-stage filters have been demonstrated. First the theory of single-stage collinear and quasi-collinear AOTF were discussed,and then the transfer function of multi-stage filter was obtained. The calculations have shown that multi-stage devices can provide significant improvement not only in sidelobe suppression but also in bandwidth narrowing as compared to single-stage ones. The triple-stage AOTF was measured,and a sidelobe suppression of about -27 dB and a narrower bandwidth were obtained. The experimental results demonstrate multi-stage AOTF is of lower sidelobe and narrower bandwidth.