The Yunshan pluton, located in the northeast of Jiuling uplift in the Jiangnan orogen, northern Jiangxi Province, consists lithologically of two- mica monzogranite.In this paper, we reported detailed studies on the LA- ICP- MS zircon U- Pb dating, major elements, trace elements, whole- rock Nd isotopic compositions and zircon Hf isotopic compositions of the two- mica monzogranite. LA- ICPMS zircon U- Pb ages show that the two- mica monzogranite was emplaced at 125. 6±1. 1 Ma and the product of early Late Yanshanian magmatic activity. The studies of petrography and geochemistry of this rock indicate that it is characterized by silica- rich, high alkalinity, peraluminous, low zircon saturation temperatures, enrichment in Rb, Th, U, K, Pb and depletion in Ba, Nb, Sr, Ti and significant negative Eu anomalies (Eu/Eu*=0. 13~0. 20). Hence, this rock belongs to highly fractionated S- type granite. εNd(t) and εHf(t) values of the Yunshan pluton vary from -3. 9 to -5. 1 and from -1. 0 to -8. 8, respectively, and the calculated two- stage model ages (TDM2) of Nd and Hf isotopes are 1. 35~1. 44 Ga and 1. 25~1. 75 Ga, respectively. Coupled with CaO/Na2O of＜0. 3，this study suggests that pelitic metasediments and minor amount of igneous rocks of Proterozoic Shuangqiaoshan Group may be the source rocks for the two- mica monzogranite. We propose that the ca. 126 Ma Yunshan granite was formed in a back- arc extensional setting in SE China during Early Cretaceous.