A real-time 3D detection method based on binocular vision is proposed to meet the high-accuracy ranging requirements of dynamic targets in low-altitude security scenarios. The method, which is based on the semi-global block matching (SGBM) algorithm, combines morphological processing, bilateral filtering, and interpolation-based hole-filling to enhance the completeness of depth information and disparity quality in weak-texture areas. With calibrated camera parameters and the triangulation principle, target 3D coordinates are computed in real time. Experiments show that within the distance range of 0.5-2.0 m, the disparity hole rate is reduced from 40.7004% to 1.2781%, with an average relative ranging error of 2.55% and centimeter-level positioning accuracy. The method’s scalability to 2000 meters is further confirmed by scale model study. Overall, the proposed system provides an efficient and cost-effective solution for multi-target 3D perception in low-altitude surveillance.