A compound tellimagrandin I with high purity (95.48%) was isolated and prepared from Aershan Rosa rugosa extract using Sephadex LH-20 column chromatography and semi-preparative high performance liquid chromatography,and its chemical structure was identified;the content of the tellimagrandin I in  R. rugosa which was determined by HPLC and its contents in 11 kinds of R. rugosa was from 0.7% to 7.4%.In the in vitro activities test,tellimagrandin I showed stronger inhibitory effect on α-glucosidase and the IC₅₀ values was 10.0 μg/mL.The extracts of R. rugosa from different areas also showed better inhibitory activities on α-glucosidase.Also,tellimagrandin I showed stronger DPPH free radical scavenging activity,and the IC₅₀ values was 8.1 μg/mL.The extracts of R. rugosa from different areas all showed DPPH free radical scavenging activities.With the contents of the tellimagrandin I in extracts of R. rugosa from different areas,the corresponding α-glucosidase inhibitory and DPPH free radical scavenging activities were tending to increase,but there was no significant correlation.This study provided a reference for clarifying the active ingredients of R. rugosa extract for lowering postprandial blood sugar,and provided a basis for the development and utilization of R. rugosa.