Based on FPGA platform, the bilinear interpolation scaling algorithm is used to realize arbitrary scaling of multichannel real-time video. DDR3 read and write logic is designed. Using ping-pong operation and multi-channel read and write arbitration module, the real-time image cache is achieved. Alpha overlay fusion algorithm is used to realize roaming overlay at any position of multichannel video and adjust the video transparency of any channel. The experimental results show that the multi-channel real-time video processing system designed in this paper can realize the maximum resolution of 3 840×2 160 and the minimum resolution of 100×100, and can flexibly change the size and position of the stacking position. The image is clear, no flash screen and no dislocation.