The tectonic geometry and kinematic dissipation of the active faults in southeast Gansu can be better understood by exploring the quantitative data of the Wudu—Kangxian fault. Based on the data from surveying and prospecting of active faults and geological mapping in Longnan City, Gansu Province, using a differential GPS, this study mainly investigates the dislocations of scarp, water system, and river terraces discovered by remote sensing image interpretation, field geological survey, fault dislocation measurement, and other basic methods. Taking some typical dislocation points for example, the ages of related terraces in the study area and adjacent Bailongjiang area were collected. The average slip rates of the west and east segment of Wudu—Kangxian fault were estimated to be 1.1 mm/a and 1.06 mm/a, respectively. According to the assessment principle and method of the maximum magnitude of potential earthquakes, using an empirical formula of M-L, it is calculated that an earthquake with magnitude 7 may occur in this area.