CoaXPress is a new high-speed digital image transmission interface standard suitable for a variety of high-speed and high-bandwidth image transmission applications. In this paper, a high-speed serial transmission system based on CoaXPress interface is designed and implemented. To solve the problem of multi-channel high-speed serial data transmission, scheduling, caching and synchronization, four CoaXPress interfaces are designed for each hardware module. The module is based on FPGA, uses PCIe3.0×8 interface to communicate with the main controller, and uses DDR4 to cache high-speed data. In FPGA firmware logic design, XDMA is used to communicate with the main controller, FDMA is used to complete the data scheduling of DDR4, and GTH is used to send and receive high-speed serial data. Based on the combination of FIFO cache synchronization technology and PXI_TRIG trigger bus technology, the synchronization between 32 transmitting interfaces of 8 CoaXPress transmitting modules is successfully realized. Finally, the CoaXPress interface module and system are tested, and the eye map, code rate, bit error rate and synchronization accuracy of CoaXPress interface meet the requirements. The high-speed serial transmission system based on CoaXPress interface designed in this paper is stable and reliable, and has been applied to the test of load-data transmission link of a new generation of space vehicle.