γ-ray irradiation technology is a new kind of physical processing method is applied in modification of starch. The influences of some factors on hydroxypropyl corn starch were investigated,including radiation dosage,starch concentration,epoxy propane dosage,sodium hydroxide dosage,sodium sulfate dosage,reactive temperature and reaction time. Then through the orthogonal experiment,the reaction conditions were optimized as follows: radiation dosage 7 kGy,starch concentration 45%,epoxy propane 12%,sodium hydroxide 1. 0%,temperature 45℃ and reaction time 8h. Under the above conditions,the molar substitution degree of hydroxypropyl corn starch was 0. 27.