Isotope chronology plays an important role in the study of Precambrian geology which lacks fossil record. In this paper, the high precision SHRIMP zircon U-Pb technique is used to date volcanic rocks in southern Anhui, in order to investigate the tectonic evolution pattern of the eastern Jiangnan orogenic belt. SHRIMP Zircon U⁃Pb dating shows that the volcanic rocks of Jingtan Formation in southern Anhui Province is 815.1 ± 7.1 Ma, The geochemical data indicate that the Jingtan Formation is island arc tholeiite. The Jingtan Formation is a magmatic arc formed on the basis of small-scale subduction of the new oceanic crust represented by the Fuchuan ophiolite in southern Anhui and its southern continental crust. In essence, it belongs to a different magmatic arc system from the Wanian group and “Pingshui Group” in Pujiang county. The eastern part of the Jiangnan orogenic belt after 850 Ma has double magmatic arcs, which is not available in the western part of the Jiangnan orogen.