By introducing the detection mode of UAV-mounted infrared and visible dual-light imaging, the non-destructive and fast detection technique of earth-rock embankment leakage is proposed for the more intuitive and efficient leakage detection of earth-rock embankments. The altitude setting of a UAV is discussed considering the imaging effect of the dual light equipment. The implementation procedure of using UAV-mounted infrared and visible dual-light imaging to detect the leakage of earth-rock embankment project is proposed, and the site detection tests of actual project are carried out under various weather conditions. The results of the tests reveal that this detection method can effectively discover the slope leakage and piping in the earth-rock embankment, and it is simple, efficient, and intuitive, with good performance at night. This detection method is excellent for the leakage inspection of large-volume and long-linear embankment projects. The limitations of this method in the practical engineering such as being affected by complex ground conditions, temperature changes, and surface sensing are also discussed.