In order to integrate and optimize the manipulation of photoelastic modulator and data processing in the measurement system of crystal electro-optic coefficient by photoelastic modulation, and realize a highly sensitive, fast, low cost and highly integral crystal electro-optic coefficient measurement scheme. According to the characteristics of the photoelastic modulation and modulation signal, a field programmable gate array is used to fulfill the control of the photoelastic modulator and the extraction of measuring data. The field programmable gate array provides the drive signal of the photoelastic modulator and controls the AD sampling simultaneously, and it also produces the cosine and sine reference sequences to achieve the DC term, the co-component and quadrature component of the first term, these terms are input in a computer to solve out the crystal electro-optic coefficient. A lithium niobate sample was tested, the results show that the repeatabilitiy and sensitivity of the system is 0.0016×10－12 m/V, the measurement rate is 1 ms/ data point. Compared to the other crystal electro-optic coefficient measurement methods, the proposed method has higher measurement sensitivity and faster measurement speed, which lays the foundation for the realization of the intelligent system for measuring the the crystal electro-optic coefficient by photoelastic modulation.