This paper reports a felsic vein in host mafic granulite from the Bashiwake area, South Altyn Tagh. Zircon grains yield a weighted mean 206 Pb/ 238 U age 491±2 Ma (MSWD=0.91). The characteristics of zircon morphology, mineral inclusions, low Th/U values, HREE enrichment, and obviously negative Eu anomalies indicate that these zircons from felsic veins were formed from the metamorphic melts. The U- Pb age of 491±2 Ma is consistent with the zircon U- Pb age of host mafic granulite, which was interpreted to be the peak metamorphic age. Thus, the felsic veins from the host mafic granulite may be formed at the peak metamorphic event. The similarity of Hf isotope features between the felsic vein and host mafic granulite indicate the melt may be an internal source, on the basis of whole- rock geochemistry, the felsic vein was generated by the partial melting of the host mafic granulite.