The Qunjisayi porphyry granite is located in Awulale area of Western Tianshan Mountains. It intruded into the volcanic rocks of lower Permian Wulang Formation located at the northwestern end of the Qunjisayi anticline. All samples from the pluton are characterized by porphyraceous texture, the phenocrysts are composed of plagioclase, potassium feldspar, hornblende and biotite, and the matrix consisting mainly of plagioclase, potassium feldspar and quartz is of granitic hypidiomorphic microcrystalline-granular texture. The porphyry granite is geochemically characterized by high SiO₂ (71.17%～72.59%)and Na₂O(8.86%～9.39%), and low K₂O(0.07%～0.28%), with A/CNK being 0.87～0.92 and A/NK 0.97～1.01. It is enriched in Th, U, Pb, but depleted in Nb, Ta, Sr, P and Ti. It is also depleted in Rb, Ba and K relative to Th and U. The porphyry granite belongs to peralkaline-mataluminous fractionated I-type granite. The zircon SHRIMP U-Pb age of the porphyry granite 302±4 Ma indicates its generation in the Late Carboniferous to Early Permian period. It is suggested that the porphyry granite is similar to the lower Carboniferous basalts in the same area, as evidenced by the following data: low initial Sr isotope ratio (I_Sr=0.705 12～0.705 36), positive εNd(t)=＋2.1～＋2.7,f_Sm/Nd=-0.43～-0.56 and the Nd model age(t_DM=713～863 Ma). In association with the tectonic background, it is inferred that the primary magma of Qunjisayi porphyry granite was most likely derived from the partial melting of the underplating basaltic rocks under the conditions of amphibolite- or garnet-phase after collision.