The mode localization effect is a proven approach for enhancing the sensitivity and resolution of MEMS physical quantity sensors. However, the lack of in-depth research on electric field introduction methods has limited the resolution of currently reported mode-localized electric field microsensors, preventing them from meeting the requirements for weak electric field detection. This study proposes a high-resolution electric field microsensor leveraging mode localization. The sensor consists of an electric field introduction structure, a three-degree-of-freedom weakly coupled resonator, and a packaging base. A floating and discrete highresolution electric field introduction design is adopted, supported by a theoretical model for optimizing structural parameters. The arithmetic square root of the amplitude ratio of the weakly coupled resonator is used as the output of the sensor to address nonlinear output challenges. Finite element simulations are utilized to analyze the vibration modes of the sensor and investigate the impact of the rotation of the electric field induction electrode on measurement accuracy. Experimental testing of the fabricated sensor under vacuum conditions demonstrates a sensitivity of 0.068 /(kV·m-1) and a background noise level of 0.012 1 (V·m-1)/Hz within the measured electric field range of 0~7 kV/m. The sensor achieves a resolution better than 0.4 V/m, representing the highest level reported domestically and internationally to date. Additionally, the sensitivity of the electric field induction electrode is tested by rotating it within the measured electric field; An in-depth study of the mode localization phenomenon in the resonator revealed that this phenomenon can be precisely controlled by selectively exciting and perturbing specific resonators to induce localization in targeted modes.