Active faults are the root causes of earthquakes, so buildings along fault lines experience the most severe damage during earthquakes. Therefore, by adopting a shallow geophysical method to accurately determine the location and distribution range of active faults and implementing effective engineering measures to evade earthquakes, we can greatly reduce earthquake disaster and consequent economic losses. The Kangding-Selaha fault is the main fault in the southeast segment of the Xianshuihe fault zone, with the tectonic condition of strong earthquakes; thus, the seismic risk in the towns passed by the fault cannot be ignored. Because the areas of the new city of Kangding that pass by the Kangding-Selaha fault are in alpine valley regions, such detection areas are subject to inconvenient traffic conditions and narrow working spaces; therefore, to obtain seismic profiles, the detection through shallow seismic reflection must be applied with small trail spacing, small displacement distance, and reception of multiple short arrangements and multiple coverage observations of common reflection points. In this study, shallow seismic detection results are combined with high-density resistivity tomography and seismic and geological survey results of the surface to reveal the spatial distribution, size, and near-surface structure of the Kangding-Selaha fault in the southeast segment of the Xianshuihe fault zone. The Kangding-Selaha fault in the southeastern section of the Xianshuihe fault zone exhibits a left-circle and right-border feather-shaped distribution in the northeast side of the new city of Kangding, and it does not only have a main cross-section. The detection results do not only provide reliable seismological evidence for determining the near-surface tectonic activity of the Kangding-Selaha fault, but also provides reliable fundamental data for seismic risk assessment, earthquake resistance planning and hazard prevention in the new city of Kangding.