In the system of the spatial light modulator, the response time of the liquid crystal under normal driving voltage is long, and the response speed of the system is slowed down. Considering these, the factors affecting the response time of the liquid crystal, the relaxation characteristics of the liquid crystal and the overdrive principle of the liquid crystal were analyzed. An overdriving method of liquid crystal based on the FPGA was put forward. Among them, phase quantization, overdriving look-up table, and PWM generation were all performed by the FPGA. This method did not occupy CPU resources and can respond to CPU instructions more quickly, and further saving LCD response time in terms of hardware. Finally, the experimental optical path was built. The experimental results show that after using the overdriving method, in a modulation period and under 5 V driving voltage, the response time of the liquid crystal modulation phase rise process is shortened from 500 ms to 35 ms, and the fall response time is shortened from 300 ms to 36 ms. The rapid deflection of the phase of the liquid crystal molecules is achieved, and the response speed of the system is improved by an order of magnitude.