In alkali catalysis condition,hydroxypropyl modified starch by using potato starch as raw material,propylene oxide as etherization reagent and sodium as expand inhibitors,are prepared through the etherification reaction.The effects of some factors such as reaction time,amount of propylene oxide,reaction temperature and amount of sodium hydroxideon substitution degree of hydroxypropyl potato starch are investigated by using the orthogonal experimental design method in order to determine the best etherificati...