In this study, the waxy maize starch is used as the raw material, propylene oxide was the etherification reagent to study the preparation and properties of hydroxypropyl starch.The effects on substitution degree and reaction efficiency by various factors such as the etherification reagent, the expansion inhibitor, the pH value, the reaction temperature and time were investigated.The results showed that with the increase of pH value, the substitution degree and reaction efficiency of waxy maize starch were increased, with the increasing of the reaction temperature, the substitution degree and reaction efficiency were increased, and with the increasing the amount of propylene oxide, the substitution degree was increased, but the reaction efficiency was in the downward trend.If the reaction time was extended.The substitution degree and reaction efficiency were in the upward trend, increasing the amount of sodium sulfate, the substitution degree and reaction efficiency were increased first and then reduced when more than 12 g sodium sulfate added.The optimum reaction conditions were as follows: waxy starch 100 g, pH value 11.5, expansion inhibitor 12 g, propylene oxide 10 mL, reaction temperature 50°C and reaction time 20 h.With the increase of the substitution degree, the freeze thaw stability, luminosity, acid resistance and viscosity and thermal stability of hydroxypropyl waxy maize starch were all increased.