Aiming at the contradiction between data processing capacity and real-time performance in current low-light-level video image acquisition and processing system, a real-time signal acquisition and preprocessing system based on FPGA is designed. The high-performance Xilinx A7 series chip is used as the main control chip. Two DDR2 SDRAM are used as the core memory device. And a CMOS sensing lens is customized as the video image acquisition device. When the hardware design of the system is completed, the engineering design and simulation analysis of the software system are carried out by Xilinx Vivado platform and Matlab. The whole process of video image acquisition, storage, processing and display in the low-light-level environment is realized. The experimental results show that the low-light-level video images acquired by the system have good real-time performance and smooth dynamic pictures.