Abstract: To speed up the modification and use of potato starch, we have studied several factors influencing graft copolymerization of methyl acrylate onto potato starch with eerie ammonium nitrate. The results show that the optimal concentration of methyl acrylate is 2. 06 mol/L and that of the initiater is 7. 298 mmol/L, the best temperature for reaction is 40℃ and the time span of reaction is between 120 and 150 mins.