Besides the widespread granitoids formed during Late Cretaceous, the late Triassic to Jurassic granites are also known to occur in the Gangdese magmatic belt. However, their petrogenesis remains a controversial issue. In this study, we conducted petrological, geochemical, zircon U-Pb dating and Hf isotopic studies for the Xiangmucun tonalites from the eastern parts of southern Gangdese magmatic belt. The tonalites consist mainly of plagioclase, quartz, biotite with minor amphibole. LA-ICP-MS zircon U-Pb dating yielded a crystallization age of ca. 184±4 Ma for the tonalites. They have positive εHf(t) values ranging from 7.90 to 10.26. The geochemical data further indicate that the Xiangmucun tonalites are middle K calc-alkaline and metaluminous, and generally show characteristics of adakitic rocks, i.e., the high SiO2, Al2O3, Nae2O/K2O (>1) and Sr/Y (35.5～105.6), low Y (4.46×10-6～12.9×10-6) and Yb (0.51×10-6～1.39×10-6), and enrichment in large ion lithophile elements (LILE) of Rb, Ba and K, and depletion in high field strength elements (HFSE) of Nb, Ta, Ti and P. They exhibit concave-upward LREE-riched and MREE-depleted patterns with negligible Eu anomalies. We suggest that the Xiangmucun tonalites were derived from the partial melting of mafic lower crust, with amphibole and garnet as the main residual phases and free of plagioclase. Combined with previous data, the zircon Hf isotopes of the Gangdese Late Triassic-Jurassic granites show a gradual enrichment trend from west to east and from south to north, which indicates that the contribution of ancient crustal components gradually increased and the ancient crust basement may exist in the eastern parts of the southern Gangdese belt.