This paper addresses the challenges of high risk, low efficiency, and poor environmental adaptability in traditional manual live-line detection for overhead transmission lines. An intelligent UAV-based detection technology is proposed, following a four-stage roadmap: “Demand Orientation—Theoretical Breakthrough—Equipment Development—Engineering Validation”. The developed airborne dual-mode multi-redundant device integrates laser sensing, multi-parameter electric field detection, and flight control algorithms to enable non-contact detection across 10kV–1000kV voltage levels. Experimental results show a reduction in detection time per tower from 45 min (manual) to 4.8 min, an 8.4 × efficiency improvement, and a 90% safety risk reduction, with 99.2% accuracy in complex conditions (e.g., 90% humidity, 5m/s wind). This technology provides a “safe, efficient, and intelligent” solution, driving the transformation of transmission maintenance toward unmanned and intelligent operations.