Neoproterozoic Hunan-Guangxi Marine Basin (Southern Hunan-Northern Guangxi, NHGMB), a remnant oceanic basin after that Paleo-South-China Ocean (PSCO) subducted to Lower Yangtze Block, was located between the South-East marginal of Middle-Upper Yangtze Block and Cathaysian Massif Group. The east segment of PSCO subduction had taken place from 1034Ma to 860Ma, the geological record was the Shaoxing-Jiangshan-Pingxiang collision zone, and so Jiangnan Island-arc Orgenic Belt had come into being. The record of PSCO west segment subducting and colliding with Upper Yangtze Block during 850～820Ma, could be distributed in the zone from Xinhua-Chengbu in Hunan to Sanjiang in Guangxi, and established Xuefeng-Sibao Island-arc Orogenic Belt, but without collision of continent to continent. The stepout of tectonic activity between the east part and the west part, therefore, was about 100Ma which had presented the space and time for NHGMB development upon the oceanic floor stopping subduction. From Pingxiang, via Chaling, to Chenzhou was a tectonic combination belt, the west side of this belt was belong to Yangtze sedimentary tectonic domain and NHGMB, deposited fine turbidite and siliceous argillite. The east side was Cathaysian sedimentary tectonic domain, including Jiangxi, Fujian and Guangdong, deposited spilite and ferriferous quartzite related to hydrothermal activity, and volcanoclastic rock. Between Chenzhou and Hexian, there was Paleo-Nanling Rift Trough (PNRT) in east-west strike, which separated Yunkai Massif, Southeast Guangdong Massif and Luoxiao-Wuyi Massif. During the Caledonian tectonic cycle, NHGMB, PNRT and Cathyasian Sedimentary-Tectonic Domain turned into Hunan-Guangxi Caledonian Fold Belt and South China Caledonian Orogenic Belt with different strike respectively.