Abstract: The study of the effects of guar gum on the digestibility and gelatinization characteristics of potato starch were reseavched used the method that simulated digestion experiment in vitro. The differences of gelatinization characteristics,thermodynamic characteristics,crystal structure and microstructure between guar gum and potato starch with the ratios of 0:100,1:80,1:40 and 1:20 were compared and analyzed,so as to explore the essential principle of the effects of guar gum on the digestibility of potato starch. The results showed when the guar gum was added lower that the system was easier to be hydrolysable and the resistant starch content was low when cooled to 37 ℃after gelatinization. With the amount of guar gum increased,the entanglement of guar gum and starch granules formed space hindrance to inhibit enzymatic hydrolysis cooledd to 37 ℃ after gelatinization,the compound system was not easy to be enzymatically hydrolyzed,and the content of resistant starch was higher. The addition of guar gum increased the initial gelatinization temperature and peak temperature of potato starch,increased the endothermic enthalpy of potato starch,prolonged the gelatinization process and increased the heat absorption. Observing the crystal structure of the compound system,it was found that no new groups were generated in the compound system after adding guar gum,the guar gum and starch were only physical effects. Meanwhile,microstructure observation showed that the steric hindrance formed by the interaction between guar gum and starch made starch particles evenly distributed,and the compound system showed a more uniform and stable structure.