Amylose content and quality are important factors in the formation of resistant starch. As indicated by measuring the amylose content in the following 6 kinds of materials such as early rice starch, kudzuvine root starch, highland barley starch, mung bean starch, broomcorn starch and lotus root starch via alkali-solution decentralization and iodine-absorbency, the amount of resistant starch obtainable is closely related to the amylose content in the materials, and is also affected by the molecule structure and the average degree of polymerization of amylose and amylopectin. Compared with iodine-absorbency, alkali-solution decentralization is superior in measuring the amylose content to prejudge the amount of resistant starch obtainable.