Abstract: The Neoproterozoic Kangdian rift basin of the western margin of the Yangtze is an important component of the Neoproterozoic rift basin system in South China. The study of its filling sequence and evolution model is of great significance to the formation and evolution of the ancient Yangtze Continent in South China.This paper reports the LA-ICP-MS U-Pb age of detrital zircon at the top of the Chengjiang Formation(PM109-51)in the mature period of the "Banxi-Nanhua Wedge Formation" in the Neoproterozoic Kangdian Rift Basin in the western margin of Yangtze, acquired 10 groups peak age, and the earliest weighted average age (723±9 Ma)is limited to represent the start time of the Chang'an ice age(Sturtian)in southern China.Comparing with the LA-ICP-MS U-Pb age value of detrital zircon at the bottom of the Early Cambrian Canglangpu Formation in the region, It is found that there is a big difference in the source contribution rate between the 801 Ma peak and the 816 Ma peak, Combined with the analysis of previous data, it is believed that during the development period of the Neoproterozoic Kangdian rift basin and even the Sinian-Early Cambrian strata without obvious changes in provenance, these performances are the source contribution of the rift basin in the early stage The rate mutation phenomenon represents the constraining control effect of the Kangdian rift half-grain basin system on the provenance.In the early stage, the old rift shoulder stratigraphy or magmatic rock provided the source.Due to the existence of the half graben basin group, the provenance contribution rate to the area away from the main boundary fault is low.As the connectivity of the half graben basin increases, the later sources are more widely radiated.