The boundary between the Cathaysia and the Yangtze blocks in the Guangxi Province has not been well constrained due to lack of exposed Precambrian basement rocks. This study presents whole rock geochemical and detrital zircon U- Pb- Hf isotopic compositions for Neoproterozoic to Cambrian meta- sedimentary rocks in the northern and eastern Guangxi Province, South China, in order to provide new petrologic evidence to constrain this boundary. The detrital zircon U- Pb dating results confirm that there are Nanhua- Sinian sedimentary rocks in the Tengxian area of eastern Guangxi Province, which were deposited later than 741~622 Ma. The Nanhua- Sinian to Cambrian sedimentary rocks in the Dayaoshao have similar detrital zircon U- Pb age spectra, characterized by a significant ~1. 0 Ga peak and a weak ~2. 5 Ga peak, similar to the basement rocks in the Nanling- Yunkai terrane, western Cathaysia Block. Neoproterozoic sedimentary rocks in the Longsheng area, northern Guangxi Province, contain abundant Neoproterozoic detritus with a main peak of ~0. 80 Ga and two weak peaks at ~2. 0 Ga and ~2. 5 Ga, similar to the Neoproterozoic sedimentary rocks in the Jiangnan Orogen, southern Yangtze Block. Neoproterozoic sedimentary rocks in the Longsheng area generally have low K 2O/Na 2O, Al 2O 3/(Na 2O+CaO) and CIA values, suggesting low maturity and weathering extent in the provenance, whereas Nanhua- Sinian to Cambrian sedimentary rocks in the Dayaoshan area have contrasting geochemical features, indicating higher maturity and weathering extent. All the major and trace element characteristics suggest that the provenance of Neoproterozoic sedimentary rocks in the Longsheng have more mafic components, similar to other Neoproterozoic sedimentary rocks in the Jiangnan Orogen, whereas the provenance of Nanhua- Sinian to Cambrian sedimentary rocks in the Dayaoshan consist mainly of felsic components, similar to the basement rocks in the Nanling- Yunkai terrane. Based on multiple lines of evidence i.e., the similarity of Hf- isotope compositions of detrital zircons in a Sinian sedimentary rock in the Dayaoshan with the basement rocks in the Nanling- Yunkai terrane and other available observations, it is suggested that the Dayaoshan area of the eastern Guangxi belongs to the Cathaysia Block, and the Longsheng area of the northern Guangxi is a part of the Jiangnan Orogen. Consequently, the western extension of the boundary between the Yangtze and Cathaysia blocks most likely passes between the Longsheng and Dayaoshan areas.