Abstract: In this paper, petrology, geochemical characteristics and U-Pb isotope chronology were comprehensively investigated to analyze the geological features of the intermediate intrusive rocks discovered in the south of Bailang County, Tibet. The results show that these rocks belong to calc-alkaline rock series, with LREE enrichment and HREE depletion; they have geochemical characteristics of intraplate basalts, being mafic intrusive body formed at the Himalayan passive continental margin stretching-compression stage in the late Triassic period. The results obtained by the authors provide new magmatic evidence for Early Tethys passive margin sedimentary basin evolution of the Yarlung Zangbo River.