To address the challenges associated with the detection of low， slow， and small （LSS） targets， a low， slow， and small target detection system based on Field Programmable Gate Array （FPGA） has been developed. This system employed a COMS camera for image acquisition， DDR3 SDRAM for video frame buffering， and utilized FPGA to process algorithms combining inter-frame differencing and optical flow. The results of target detection were presented using the VGA standard. Test outcomes verified the system's capability to detect and real-time display low， slow， and small unmanned aerial vehicle （UAV） targets in hovering and low-speed flight postures.