Abstract: In order to meet the requirement of real-time compression and transmission of the high speed video data derived by micro-nano remote sensing satellite, this paper proposes a small scale implementation method of real-time H.264 video encoding. The system hardware consists of the high performance programmable logic device (FPGA) and H.264 encoding unit (DSP), both with space quality assurance, which can be implemented on a 6U VPX standard module to support 4K ultra high definition video compression. The programmable logic device mainly accomplishes the standard Camera Link interface protocol parsing , the video frame splitting, and the standard Video Port interface protocol conversion of the ultra high definition video data. Under the scheduling of real-time multitasking operating system, the H.264 encoding unit mainly accomplishes the video block mosaic and the real-time video compression based on the H.264 algorithm. The results of the video quality assessment and the in-orbit application indicate that the compression capacity of a single 6U video compression unit is achieved up to 2.5Gbps, and the Peak Signal Noise Ratio (PSNR) result is clearly superior to 36.6dB with the compression ratio of 50:1, 20:1 and 10:1. Refer to the five-grade quality scale in Recommendation ITU-R BT-500-11, the “excellent” video quality is achieved. This implementation is suitable to apply in micro-nano video remote sensing satellites, and it has been applied to the OVS-1 video observation satellites successfully.