Abstract: The amphoteric polymer flocculant with anion and cation was syn thesized with starch-g-polyacrylamide by Mannich reaction and hydrolysis. The optimum reaction condition was obtained as follows: the molar ratio among gr aft polymer, formaldehyde to dimethyl amine was 1∶1.1∶1.5, mass concentrati on of graft polymer 2.5%, temperature of methylamine reaction 50 ℃, reaction time 2.5　h , cationic degree 50%; the mass ratio of sodium carbonate to sodium hydrox ide 1.4∶1, the molar ratio of hydrolytic agent to graft polymer 1∶1, hydro lytic temperature 65 ℃, hydrolytic time 3 h, anionic degree 23%. The turbid ity an d chemical oxygen demand (COD) removal rate of this product for dyeing factory a nd paper mill waste water are better than those of HPAM.

Key words: starch, amphoteric high molecule flocculant, cationic degree, anionic degree