The invention relates to the field of power transmission and transformation line fault finding devices, and particularly relates to an overhead line earth fault finder used for single-phase earth fault finding of a 10KV power transmission and transformation line. The overhead line earth fault finder is characterized by comprising a lithium battery power supply, a device voltage sampling loop, an A/D sampling circuit 1, a low-frequency signal source, a low-frequency power amplifier circuit, a low-frequency signal sampling loop, an A/D sampling circuit 2, a high-frequency signal source, a high-frequency excitation circuit, a high-frequency signal sampling loop, an A/D sampling circuit 3, a DSP unit, a main CPU, a main wireless signal communication unit, a keyboard and interface circuit, a liquid crystal display unit, a sound-light alarm output unit, a child wireless signal communication unit, an earth inductor, an induction signal processing unit and a child CPU. The device is used for rapidly and accurately locating the earth point after power outage of the 10kV fault line so that rapid finding under the condition of fault of distribution network equipment can be realized. The labor intensity of line maintenance personnel can be reduced, time and labor can be saved and the working efficiency, the power supply reliability and the economic benefit of the electric power enterprises can be enhanced.