High-definition and high-speed raw video data are large, so the traditional GigE and USB 3.0 transmission cannot meet the requirements. Double SDI is used to transmit high-speed video images from front-end high-definition and high-speed camera to back-end receiving equipment for processing. It has the characteristics of low cost, simple interface circuit and private protocol. The key idea and implementation method are to convert a non-standard 2048 * 2025@100fps high-definition and high-speed monochrome image video format into a standard high-definition video format, and use double 3G-SDI interface and coaxial cable for high-speed video transmission. In the whole process, high-speed images in non-standard format can not only maintain the integrity of the original video but also complete correctly. The monochrome 2048 * 2025@100fps raw data are recorded and outputted, which realize the long-distance lossless transmission. The technical route of lossless image transmission in this paper can be effectively applied to other high-definition and high-speed real-time transmission systems. © Springer Nature Singapore Pte Ltd. 2020.