Abstract: The aseptic seedlings of Astragalus sinicus were treated as two groups.One group was inoculated by Rhizobium astragalus and the other was designed as contrast without inoculation.These two groups were all cultivated in sterilized cultured liquid about one week.The root segments which have distinctive deformation of root hairs from first group were cut off and be fixed,meanwhile the corresponding root segments were cut off from the contrastive group and be fixed.These groups of roots segments were treated as semi-thin section and ultrathin sections,and then were observed by optical microscope and transmission electron microscope.The result shows:the transfer cells with wall ingrowths on the tangential exowall of the root epidermal cells is easy to be found in the root segments which has distinctive deformation of root hair.The wall ingrowth lies not only in root epidermal cells but also in the root hairs,while there is no wall ingrowth in root epidermal cells of Astranalus sinicus which is not inoculated by rhizobia.This proved that the forming of transfer cells in epiderm of Astragalus sinicus was due to the inducement of rhizobia of Astragalus sinicus.