The Tangtang granite occurs in the western margin of the Yangtze platform and mainly consists of plagioclase granite. In order to reveal the significance of its petrogenesis, the authors studied the SHRIMP U-Pb dating of zircon and geochemistry of the granite. It is suggested that the granite was formed by partial melting of argillaceous rocks in the crust. The pattern of bimodel magmatic rocks and the Al₂O₃-SiO₂ diagram both indicate that the formation of Tangtang granite was closely related to the rift environment. The result is consistent with the tectonic setting of 1.0 Ga in the western margin of the Yangtze platform and also corresponds to the Rodinia supercontinent convergence