A novel intense electric field optical sensor based on Fabry-Perot interferometer utilizing LiNbO3 crystal is proposed and demonstrated. Compared to the traditional bulk-type electric field optical sensors, this sensor unit requires only a LiNbO3 and two collimators, eliminating the need for quarter wave-plate and allowing for measurement of electric field without limitation by half wave voltage. The Vernier effect, generated by birefringence of LiNbO3, is utilized to enhance the sensitivity of electric field measurement, which does not require additional reference cavity. Both theoretical and experimental results illustrate that the wavelength shift of the sensor is linear function of the measured electric field. In the range of 0∼1010 kV/m, the sensor's measurement sensitivity is 2.22 nm/E (V/µm) with detection limit of 1.27 × 10-2 E. Additionally, an MZI is proposed for temperature compensation, resulting in a standard deviation of spectrum variation after compensation of only 5.01 × 10-3. Applications using this sensor confirmed that it is expected to find widespread use in measurements of intense transient electric fields.