Combined with Maxwell’ s equations, a mathematical model of light propagation in electro-optic crystals was established; physical parameter models of lithium niobate crystal and bismuth germanate crystal were established through finite element simulation, and a universal three-dimensional wave field simulation method of incident light was proposed. This method combines the electric field distribution inside the crystal with the coupled wave theory of the electro-optic effect, and calculates the Pockels effect of the two crystals under transverse modulation. The difference between the results and the theory is within 10 -5 orders of magnitude; at the same time, the simulation results show that the Pockels effect of lithium niobate crystals is more obvious. Finally, 0 ~ 1 000 V DC voltage experiments are carried out on two electro-optic crystals of different materials. The experiment shows that the measurement accuracy of the Pockels effect of the lithium niobate crystal is better than ±2. 9%. This method provides new research ideas and theoretical references for the selection and performance evaluation of electro-optic crystals for optical voltage sensors.