Cenozoic volcanic rocks distributed at the Hoh Xil Mts. belong to eastern segment of the Cenozoic volcanic rock belt outcropped along the north Tibetan plateau. In this area volcanic rocks occur mainly in the forms of lava plateau and table mountains, about 40 100m in thickness. Excepting a few high-K 2O rhyolite, trachydacite and trachyte, latites commonly having clino and orthopyroxenes phenocrysts are superior in quantity and distribution. These volcanic rocks are characterized by enrichment of alkalis (specially K 2O) and REE. The volcanic activity took place only in Miocene and might be divided into early (17.3 15.4Ma), middle (14.5-11.7Ma) and late (7.5-6.95Ma) stages based on K/Ar dating. Petrological and geochemical characteristics and ages of volcanic rocks in the Hoh Xil Mts. are consistent with those of Cenozoic volcanic rocks in Tibet. The volcanic activities have been closely related to the lithospheric evolution of the Tibetan plateau since Cenozoic.