Abstract:High amylose corn starch as raw material， through the heat treatment preparation of pregelatinized starch， and citric acid were esterified. Using in vitro model， Fourier transform infrared spectrometer（FTIR）， scanning electron microscopy（SEM） and thermogravimetric analysis（TG） of two straight chain starch proper－ ties high difference method. The results showed that compared with the raw starch， pregelatinized starch more significantly improve the degree of esterification and reduced its digestibility. Comparison of two kinds of esteri－ fied starch， citric acid esterification pregelatinized starch will lead than raw starch citric acid esterification were lower the rate of digestion， the low digestibility was associated with high degree of substitution， its relevance was verified by absorption characteristics of Fourier transform infrared spectroscopy. At the same time， TG anal－ ysis showed that citric acid esterification of pregelatinized starch and its thermal decomposition at high tempera－ ture， Thermal stability was stronger. These structural characteristics may be related to its low digestibility. The further study of this study had a certain guiding significance for the further improvement of resistant starch con－ tent in starch.