Abstract：It is widely believed that there were double strata (or three strata) of Pre-Sinian period of Western Margin of Yangtze Terrane, which could be divided into the lower crystalline basement and the upper fold basement. Hekou group was recognized as a transition layer between these two, and its property and age were still having much controversial. Advanced study of Hekou Group would have important implications for understanding of the feature and evolution of the basement structure of Western Margin of Yangtze Terrane. Here we reported 13 groups of zircon SHRIMP U-Pb ages from the diabase that intruded into Hekou group, and obtained 1710±8Ma concordant U-Pb age, which indicated that Hekou group was formed earlier than that age. According to large numbers of previous isotopic ages, Hekou group should be formed during 1817-1710Ma, later Paleoproterozoic.The age of the diabase reported in this study, has confined the upper limited age of Hekou group, and has great significance in further research on the Precambrian tectonic stratigraphy, formation and evolution of Yangtze Terrane.