Cyanobacterial blooms have become a serious pollution problem, in particular, for water resources. Microcystis aeruginosa (M. aeruginosa) is most common toxic cyanobacterial bloom in fresh waters. In this paper, SnO2-montmorillonite composite was prepared by ion exchange method and applied to remove M. aeruginosa with the assistance of UV-light. The structure of the resulting composite was identified by XRD, IR and TEM. It was determined that some SnO2 nanoparticles were inserted into the interlayer of montmorillonite and some were dispersed on the surface of montmorillonite. M. aeruginosa removal efficiency was judged by the rate of 95％ after treatment with 0.3 g/L SnO2-montmorillonite for 1 h. SnO2-montmorillonite composite absorbed M. aer-uginosa and promoted M. aeruginosa lysis by damaging cell wall and membrane. The cellular contents, including protein and chlorophyll a, were then degraded with the assistance of UV-light, which inhibited the biological activity of M. aeruginosa. In fact, SnO2-montmorillonite composite removed M. aeruginosa by combination of adsorption flocculation and UV-induced catalytic degradation. SnO2-montmorillonite shows promise to become an effective material for the removal of algae and the cyanobacteria bloom.