In　order　to　acquire　the　failure　mechanism　and　anti-collapse　measures　of　masonry　structures　under　debris　flow,　this　paper　established　a　three-dimension　fluid-solid　coupling　finite　element　analysis　model　by　means　of　the　finite　element　software　LS-DYNA.　The　failure　mechanism　of　masonry　structures　under　debris　flow　were　investigated　by　observing　the　deformation　of　structure,　the　energy　of　system　and　the　displacement　and　velocity　of　key　points.　According　to　the　failure　mechanism　of　masonry　structure　and　referring　to　the　current　codes　and　engineering　practice,　three　anti-collapse　measures　were　proposed,　including　increasing　constructional　column　section　size,　reducing　housing　width　size　and　lowering　the　structure　height.　The　numerical　results　show　that　the　plastic　deformation　of　constructional　columns　can　be　reduced　insignificantly　by　reducing　housing　width　size　and/or　lowering　the　structure　height;　the　impact　resistance　of　masonry　structure　can　be　effectively　increased　by　increasing　the　section　size　of　constructional　columns.　©,　2015,　Tsinghua　University.　All　right　reserved.