Abstract: The Wannian Group is a low- grade metamorphic series of the Mesoproterozoic Jixian Period in the Jinxian- Wanni- an area,northeastern Jiangxi,in the Jiangnan composite migmatite belt. According to its rock association and sedimentary envi- ronment,the group may be subdivided in ascending order into the Fengshuling Formation,Niutouling Formation,Piku For- mation and Chengyuan Formation. The rock geochemistry reflects that: its tectonic environment was the continental island arc- back- arc basin, and its horizon is equivalent to the Anlilin Formation, Xiushui Formation and Xikou Formation of the Shuangqiaoshan Group- complex, Shuangxiwu Group- complex of the volcanic arc and Zhangcun Group- complex of the back- arc basin but their rock associations are quite different,belonging to the synchronous and heteropic products. The estab- lishment of the Wannian Group provides a new idea for the stratigraphic division and correlation of the Mesoproterozoic strata in South China.