The invention discloses a method for preparing stable slow-digestion starch and belongs to the field of modified starch processing. The principle of the method is that: rice starch is degraded to form short chain straight chain starch based on high-power ultrasonic waves, and a single spiral V-shaped microcrystalline starch-lipid complex is formed through high-temperature lipid reaction and short-term crystallization, and has obvious slow-digestion characteristic. The method for preparing the stable slow-digestion starch comprises the following steps of: treating rice starch milk for 25 to 30minutes under the ultrasonic conditions of the frequency of 500 to 600 W and the temperature below 25 DEG C, and adding lipid (the rice accounts for 20 to 22 mass percent) for performing high temperature complex reaction for 20 to 25 minutes at the temperature of between 140 and 160 DEG C; and obtaining the product containing over 70 percent of the slow-digestion starch and of which the residual slow-digestion starch is over 95 percent in high-temperature processing treatment (at the temperature of between 90 and 110 DEG C) by adopting the short-time crystallization technology (at 4 DEG C for12 hours). The method has the advantages of good product quality, high nutritional value, low glycemic index, low production cost, easy continuous production, no environmental pollution, wide market prospect, and high social and economic benefits.