A resistant dextrin and prepration method therefor. According to the resistant dextrin, the molar content of DP1 is smaller than or equal to 1%, the molar content of DP2 is less than or equal to 4.5%, the molar content of DP3 is less than or equal to 7.0%, the average degree of polymerization is 6-12, the pH value is 3.0-6.0, and the molar content of dietary fibers is more than or equal to 85%. According to the preparation method of the resistant dextrin, starch is used the raw material, a dextrinization reaction is divided into two stages for the first time, and the degree of polymerization of the polymerization reaction is powerfully guaranteed; meanwhile, generation of side reactions is reduced, and the subsequent treatment difficulty of purification is greatly reduced.
