Whole-rock Sm-Nd isochron ages and Nd model data of six samples from theXiongsong Group metamorphic rocks in the middle sector of the Jinsha River arereported here. The results show that the isochron ages of muscovite-biotite schistis 1 594 Ma, the Nd model ages may be classified into two groups: their averageages are 1 723 Ma and 2 011 Ma respectively. The diagenetic age of the XiongsongGroup appears to be 1 594 Ma. The Nd model ages of 1 723 Ma and 2 011 Ma arevery close to those of the continental crust of southern China (the reaches of theJinsha River and the Yangtze River). The present Xiongsong Group metamorphicrocks of western Sichuan and eastern Tibet might belong to continental crust ofsouthern China. They might be initially formed in the early Proterozoic or evenearlier.