A　novel　condensation　polymer　starch-base　cationic　polyelectrolyte　(S-FAD)　was　synthesized　by　grafting　a　copolymer　of　formaldehyde,　acetone　and　dimethylamine　(FAD)　onto　cassava　starch.　S-FAD　samples　were　characterized　by　FT-IR,　XRD　and　elementary　analysis.　The　optimum　synthesis　condition　was　determined　by　investigating　the　cationicity　and　the　color　removal　performance　of　the　cationic　starch.　Their　performance　as　a　cationic　flocculant　in　removing　three　anionic　azo-dyes　from　simulated　dye　wastewater　was　evaluated.　Results　showed　that　the　optimum　conditions　were　as　follows:　reaction　temperature　65　°C,　the　mole　ratio　of　formaldehyde　to　dimethylamine　and　acetone　to　dimethylamine　were　4　and　1.2　respectively,　the　dose　of　starch　was　5　g.　Under　this　condition,　the　cationicity　of　the　product　can　reach　3.40　mmol/g.　The　coagulation-flocculation　properties　were　excellent　under　acidic　and　neutral　conditions　and　the　decolorizing　rates　were　above　98%　©　2011　IEEE.