As an important electrical parameter characterizing the state of power transmission lines, accurate voltage measurement is essential to ensure the reliable operation of transmission lines. Aiming at the traditional non-contact voltage measurement method based on the principle of electric field coupling, which is easily affected by environmental changes, has poor anti-interference ability, and the voltage amplitude cannot be measured accurately, this paper proposes a non-contact voltage measurement method based on the topological transformation. The method adopts differential electric field sensing probe to improve the anti-interference ability of the sensor, and solves the problem that the voltage amplitude cannot be measured accurately due to environmental changes by topology transformation. In this paper, the working principle of the voltage measurement method is first analyzed, and then the feasibility of the method is verified through simulation. On this basis, the design of the sensor signal conditioning circuit is completed. Finally, the sensor prototype was tested. The experimental results show that the amplitude relative measurement errors of the sensor prototype in the ranges of 0.5–1.5 kV and 1.5–5 kV are within 1% and 0.6%, respectively, and the phase error is kept within ±0.2°, which has a high measurement accuracy.