Abstract: UHV converter station is prone to produce switching overvoltage during switching operation, However, due to its high voltage level, strong electromagnetic interference and other factors, there is still no effective means to measure the overvoltage. Therefore, a study is carried out on the switching overvoltage measurement by refitting the capacitive voltage transformer (CVT). By establishing a CVT series voltage division model, the influence of electromagnetic unit on the overvoltage measurement is simulated, and the feasibility of refitting is demonstrated. The internal structure of sensors is optimized to reduce stray parameters, consequently improve the anti-interference ability of the sensors. The outer shielding, signal cable matching, shielding and grounding of the measurement system are optimized to effectively collect the overvoltage signals under strong electromagnetic interference. A field test was carried out in the ±800 kV UHV Shaanbei Converter Station, and the switching overvoltage during switching the no-load line and the low-voltage reactor was effectively recorded. In a word, an overvoltage measurement system is developed for the UHV converter station, and the effectiveness and safety of the design scheme is verified through field tests. This work is supported by Science & Technology Project of State Grid Shaanxi Electric Power Research Institute (Research on Overvoltage Test Technology in Complex Electromagnetic Environment of ±800 kV Converter Station-Sensor and Electromagnetic shielding Design Optimization Research, No.SGTYHT/19-JS-217).