The invention provides a system for detecting the maximum power-taking power point of a high-voltage overhead ground wire. The system comprises a power supply unit, a current transformer T1, an impedance-adjustable load unit and a detection output unit, wherein the power supply unit is used for generating power frequency sine alternating currents and loading the currents to two ends of the overhead ground wire, two ends of the primary coil of the current transformer T1 are respectively connected to two ends of the overhead ground wire, two ends of the secondary coil of the current transformer T1 are connected with two ends of the impedance-adjustable load unit, and the detection output unit detects voltage at two ends of the impedance-adjustable load unit and currents passing the impedance-adjustable load unit and calculates a power-taking power value according to the detected voltage and currents. By the structure, the system has the advantages that the maximum power-taking power point of the overhead ground wire can be detected accurately, electric energy generated on the overhead ground wire through induction can be fully utilized, electric energy waste is prevented, a sufficient electric energy guarantee is provided for the monitoring equipment and grid nodes of a power grid, and potential safety hazard caused by the direct power taking on a power transmission line is avoided.