In order to meet the challenges of transient electromagnetic exploration in complex terrain, a lightweight, low-noise, three-component, fully-airborne transient electromagnetic system is designed based on an unmanned aerial vehicle platform. By receiving the three-component electromagnetic field, reliable detection of the normal component even in undulating terrain is enabled, while also offering a theoretical basis for correcting errors arising from receiver coil oscillation. Through a system-level optimization design, the system balances weight and transmission power, resulting in a lightweight (14.94 kg), large transmitting magnetic moment (2250 Am²), and extremely low system noise (1.7 nT/s) configuration. A series of performance verification experiments and field tests verify the stability and practical operability of the proposed system in field applications. Comparisons between the inversion results of the collected detection data and borehole logging data further confirm the reliability of the system. Therefore, this system can provide an effective technical approach and solid data support for the fine detection of subsurface interfaces within a depth of 50 meters.