In this paper， Phaseolus radiates L. starch as the raw material， the Phaseolus radiates L. resistant dextrin were prepared by acid hydrolysis method， and were purified by the sequential simulated moving chromatography （SSMB）. The optimized process parameters were： feed rate 455 g/h， water consumption 682 mL/h， circulation quantity 346 mL. Under these conditions， the purified Phaseolus radiates L. resistant dextrin concentration was 24.6%， the purity was 99.17%， and the yield was 91.31%. Molecular characteristics of Phaseolus radiates L. resistant dextrin were analyzed by the SEM， FTIR， XRD， SEC-MALS and GC-MS， it had high purity and excellent molecular characteristics， it could provide theoretical principle for the development and utilization of resistant dextrin.