The Chengxian-Xiji profile of DSS in Tianshui earthquake area is from Chengxian country of province Gansu to Xiji country of Ningxia Hui Autonomous Region,the total length of profile is 242km with 4 shots.The crust can be divided into four layers,sedimentary,upper crust,middle crust and down crust.The deep of Moho increase gradually from south to north,and it rises in the vicinity of Tianshui-Qinan.The low velocity layer (LVL) was found in the top of middle crust.The northern fringe fault of western segment of Qinling Mountain across to the profile is a over-crust fault and it is a boundary fault between Qilian and Qinling Geosyncline.