The Sibao Group in South China is an important part of the Jiangnan Oregenic Belt, it’s a “window” to recognize Jiang Oregenic Belt’s trench—arc system. we use sedimentology to study its prototype basin and tectonic paleogeographic pattern. Based on these works, we have five following understanding:① The Sibao Group, in Southeast of Guizhou, is an upwardshallowing sequence.Yaodeng Formation is deep sea—bathyal mudstone and turbidite; The upper of Hecun Formation is neritic clastic, the lower of Hecun Formation is shore facies. Sibao Group, in north of Guilin, are turbidite facies, and the Bouma sequence are developed.② The rose diagram of inclined bedding in clastic of Sibao Group, in north of Guilin, show that paleocurrent direction Pointing to the south, the provenance is from the north.③ Statistical results of skeleton particles show that the tectonic feature of the provenance of Sibao Group is Magmatc Arc.④ Based on the above findings, we suggest that the tectonic environment of Sibao Group’ clastic rocks is forearc basin.