U-Pb isotopic ages of four Early Praterozoic granitic bodies in southern Zhejiang have been determined:Xiaji admellite 1975士180Ma, Lizhuang adme- llite 1870士136Ma, Tianhuo granodiorite 1832士80Ma, and Sanzhishu migmatite 1863士144Ma, These data show that the rocks of the Zhejiang-Fujian Preca- mbriari metamorphic basement underwent an intense magmatic thermal event in the period of 1875士100Ma.This magmatic thermal event, which resulted in migmatization, granitization and magmatic intrusion in the basement rocks, played an important role in the formation of Zhejiang-Fujian stable crystalline basement. These results also suggest that the formation of the host rocks of the granitic rocks, namely Badu (Mayuan) Group, occured be- fore 2.OGa. The 1863士44Ma U-Pb age of migmatite and 2071士48 Sm-Nd iso- chron age of amphibolite in Sanzhishu demonstrate that at least part of the "Hexi" Group is of Early Proterozoic rather than Late Paleozoic. The meta- morphic rocks in Sanshishu may be a part of Zhejiang-Fujian metamorphic 'basement.