The southern Xiaochangshan granitic intrusive is an important geological body in Beishan tectonic belt, Xinjiang, produced by the second sequence magmatic intrusion in the middle Hercynian period. The superunit is composed of five units covering an area of about 132.9 km2. The isotopic geological age of the fourth unit is 320.2±23 Ma (zircon, lead-lead age method). The rocks are of calc-alkaline series and belong obviously to the comagmatic evolutionary sequence. Trace elements show characteristics of the mature arc granite in the background of the land arc and I-type granite. The superunit was formed by the strong magmatic intrusion during the closing period of Beishan craton rift valley.