For an integrated electro-optical sensor, the operating point has a significant effect on the performance of the sensor. In this paper, an optical waveguide electric field sensor with controllable operating point is designed using LiNbO₃ materials, which has an asymmetric Mach-Zehnder interferometer (MZI) structure. Theoretical results show that the optimal operating point can be obtained and controlled by tuning the output wavelength of the tunable laser used in the sensing system. The simulation results show that the sensitivity about 83 dB·μV/m can be obtained, and the linear dynamic range as large as 60 dB can be achieved. And the fabrication tolerance of the center-to-center distance for the 3 dB coupler used in the asymmetric MZI is ~0.5 μm, while the power splitting ratio of the Y branch is with more tolerance.