Abstract: The Hexi Corridor,located in the northeastern margin of the Qinghai-Tibetan plateau,is a foreland basin system formed by the northeastward push of the plateau.The Yumu mountain is a transverse highland between the Zhangye basin and Jiudong basin in the system.Based on the field study of fault outcrops and landform deformations,combining with TL and ¹⁴C ages,it is concluded that the north marginal fault of the Yumu mountain is a thrust with left-lateral slipping and the east marginal fault is a thrust with right-lateral slipping,and the Yumu Mountain developed from the resulting uplifting of the Yumu Mountain block along these faults.