The optimum conditions for the preparation of kidney bean resistant starch by ultrasonic-microwave synergistic enzymatic method and the structural characteristics of kidney bean resistant starch were investigated. Purple round kidney bean starch was used as experimental material， and RS3-type resistant starch was prepared by ultrasonic-microwave and pullulan enzymatic hydrolysis method. The effects of different levels of starch suspension mass fraction， ultrasonic time， pullulanase addition and microwave power on the yield of resistant starch were investigated， and the response conditions were used to optimize the process conditions， and the structures of kidney bean starch and resistant starch were analyzed by gel permeation chromatography， scanning electron microscopy and infrared spectroscopy characteristic. The results showed that the highest yield of the resistant starch of alfalfa was（24.37 ± 0.41）% when the mass fraction of starch suspension was 16%， the amount of pullulanase was 12.5 ASPU/g（dry basis）， the microwave power was 300 W， and the ultrasonic-microwave synergistic treatment for 20 min. Compared with the original starch， the resistant starch granules of kidney bean were broken and showed different shapes and sizes like a block of gravel structure. There was no new characteristic absorption peak of resistant starch. The average polymerization degree of resistant starch in kidney bean was decreased after treatment， the weight average and number average molecular weight increased， and the polydispersity coefficient decreased. Ultrasound-microwave synergistic enzymatic hydrolysis could increase the yield of resistant starch in kidney bean. The starch functional group unchanged during the formation of resistant starch， and the other structural characteristics changed.