The Yumen fault, as a part of the northern Qilianshan fault zone, is a branch of the south-margin fault of the Jiuquan basin and also the boundary of the second-order structural element in this basin. The Yumen fault is characterized by intense thrusting and napping from south to north with relatively small sinistral displacement. The sense of the strike-slip of the secondary faults inside the Yumen fault is related to the trend of the faults. The Yumen fault has been active since the Early Pleistocene to the present day, so it is an active fault during the Holocene Epoch and a causative fault of the Yumen earthquake.