The Dangra Yun Co and Xuru Co NS-trending graben located at central section of the Gangdese, is controlled by NS-trending high-angle normal faults and consists of the Dangqung Co, Dangra Yun Co and Xuru Co. Miocene alkati volcanic rock distributed along the graben indicates an intraplate extensional tectonic environment by its petrochemical and geochemical analyses. The Dangra Yun Co and Xuru Co graben, as well as other NS-trending grabens, is the results of extension of upper crust driven by the thermal upderplating of the lower crust flowing and thickening. S-N extension became E-W extension with the change of flow direction in the lower crust.