During the middle and late stages of oilfield development in China, crude⁃oil water cut tends to increase, adversely affecting both crude⁃oil production quality and oilfield development efficiency. Accurate measurement of water cut is essential for crude⁃oil processing, transportation, and storage; therefore, real⁃time and precise water⁃cut measurement is of considerable practical importance in oilfield production. To address the challenge of accurately measuring high⁃water⁃cut crude oil in real time, an optimized five⁃electrode measurement configuration was developed for an annular⁃array conductance sensor based on the conductance method. First, the sensor dimensions and structural parameters were optimized through sensitivity analysis using MAXWELL simulation software. Next, a signal excitation circuit and a signal processing circuit were designed to ensure measurement stability and data accuracy. Finally, experiments were conducted to measure the water cut of high⁃water⁃cut crude oil. The results show that the proposed method provides high measurement accuracy, requires simple peripheral circuitry, and exhibits strong resistance to electromagnetic interference. In addition, the system measurements closely follow the actual variation in water cut, with relatively small overall errors and good stability and repeatability.