Abstract: In order to realize the direct measurement of high-voltage line voltage harmonic signals, the method of directly obtaining high-voltage line voltage harmonic signals based on space capacitance effect was studied, and a high-voltage line harmonic detector was designed, which can realize the accurate measurement of 2~32 even harmonics and 3~31 odd harmonics, the detector includes a harmonic signal acquisition device and a receiving device, and the harmonic information is transmitted between the two through wireless radio frequency, which realizes the physical isolation between high voltage and low voltage, so that the detector is safer and more convenient to use. After actual on-site comparison and testing, the measurement accuracy of the harmonic detector meets the design requirements.