An optical voltage transducer (OVT) for the electric power system based on modular interference in dual-mode highly elliptical-core polarization maintenance fiber (E-core PMF) is designed, and the temperature and environmental perturbation can be compensated automatically. A quartz crystal cylinder wrapped with highly elliptical-core fiber plays the role of voltage sensor head. The two interference output lobes′ intensity from the E-core PMF is modulated with the converse piezoelectric effect of quartz crystal. A PZT wrapped with E-core PMF at ground potential serves as the static modular phase difference control and temperature compensation unit. The experimental results show that the measurement precision of is 0.5% near by rated voltage, and the OVT has a good linearity when measured voltage is greater than 10 kV.