The Yifeng Formationin the southern margin of the Jiuling uplift in northwestern Jiangxi is an important stratigraphic unit in the Jiangnan orogen, South China, but its depositional age and regional stratigraphic correlation is uncertain. During the 1∶50000 regional geological survey, intercalated metamorphic andesite and tuff was discovered in the Yifeng rock formation in the WanzaiYifeng area. SHRIMP zircon dating indicates that the metamorphic dacite and metamorphic tuff formed at 835+7.8 Ma and 830.3+9.5 Ma respectively. Combined with the youngest detrital zircon UPb age of 852.9+2.6 Ma for the tuff from the bottom of the Yifeng Formation, it can be believed that the Yifeng Formation deposited at ~853 Ma, indicating that the main rocks of the Yifeng Formation formed in the early Neoproterozoic. Zircon Hf isotope composition shows that εHf(t) has a wide variation range from -16.02 to +12.04 and is generally positive. The εHf(t) values of five zircons with most similar compositions of mantledepleted mantle range from +9.65 to +12.04, and have the youngest Hf two stage mode age (TDM2) of 0.95~1.09 Ga, which is close to the diagentic age, indicating the new crustal materials may be involved in the provenance. Regionally, the field sedimentology study shows that the turbidite sedimentary structure of the Yifeng rock formation is well developed with the main rocks belonging to the bathyal deposition of continental slope. The Yifeng Group basically has similar sedimentary ages and similar sedimentary environment as the Xikou, Shuangqiaoshan, the Lengjiaxi, Xicun, Nanqiao and Cangxi groups have. It can be concluded that they should be the one set of backarc basin sequence underlying the unconformities of the Jinning orogeny and overlying the Shuangxiwu arc strata in South China.