Abstract: The evolution of the Bangong Co-Nujiang River Tethys Ocean has long aroused much interest among geologists. The polarity of its subduction remains a topic of much controversy. This paper reports the geochronology, geochemistry and zircon Hf isotopic data of the Late Jurassic diorite in Rongma area, southern Qiangtang terrane, Tibetan Plateau. The LA-MC-ICP-MS U-Pb dating of zircons yielded an age of 149.7±0.8Ma. The Late Jurassic diorite is characterized by rich alkali metals, poor MgO, TFeO, CaO, enrichment of LREE as well as Rb, Th, U, K elements and depletion of Ta, Nb, P, Ti elements. The positive zircon εHf(t) with the wide range (+4.26~+9.29) indicates the mixing of mantle and crust magma. These new data, together with the geological background, indicate that the Late Jurassic diorite in Rongma area was formed by mixing of mantle and crust magma in response to northward subduction of the Bangong Co-Nujiang River Tethys Ocean.