Abstract: Zircon dating age of tuff bedding from the Sibao Group in Guangxi and Guizhou provinces is firstly reported in this paper. Integrating the zircon SHRIMP U-Pb dating of the granite which intruded into the Sibao Group, the group is thus determined to be Neoproterozoic. The Sibao Group (same as the Fanjingshan, Lengjiaxi and Shuangqiaoshan groups) and the Danzhou Group (same as the Xiajiang, Banxi and Heshangzhen groups), which are slightly metamorphosed rocks are well developed in the Jiangnan Orogen, formed a metamorphosed basement of the Jiangnan old land. Many years ago, the Sibao Group was categorized into Mesoproterozoic, and it was main part of the Sibao Movement. The age of Sibao Group is still influencing the strata subdivision and correlation for the metamorphosed rocks in whole Jiangnan old land and has restricted the Chinese geologists to resolve the geological background and mineralization condition of the Jiangnan Orogen. In zircon study from bentonite in the Sibao Group, we've accurately determined the zircon dating of 841.7 Ma±5.9 Ma in the group and intruded granite zircon dating of 826.8 Ma ± 5.9 Ma from the Mt. Motianling.