The late Indosinian Nanyili granite, exposing in the southern margin of the Bikou area, was analyzed and discussed so as to better understand its genesis, oreforming material source and structural setting. The results show that the Nanyili granite is high in SiO2(71.29％～73.05％) and Al2O3 contents, slightly low ratio of FeO/(FeO+MgO), has A/CNK ratios ranging 1.07～1.11. All these characteristics suggest sthat it belongs to typical peraluminous granite. The ∑REE ranges from 56.80×10-6to 89.12×10-6, REE diagram shows rightward incline and obvious negative Eu abnormity. High field strength elements such as Ta、Nb、P and Ti show distinct nagetive anomly while lithophile elements such as Rb and Sr exhibit obvious positive anomalies. Magma source is probably rising and emplacement of partially melt granitic magma dominated by greywacke, which is typical of crustal genesis. With the features of the postcollisional magmatic activity, the Nanyili granite is the product of partially melt crust in such a geologic condition of crustal thickening resulted from the collision between the North China massif and Yangtze massif during the Indosinian. It formed during the transition period from syncollision (compressional) to post collision (extensional environment).