SpaceWire is an onboard data-handling network for spacecraft which offers high-speed, low power, simplicity, low cost, and architectural flexibility. The unit uses SpaceWire protocol to implement high speed image data transmission for space application. The FPGA can control the system to realize initialization and handling of data packets transmission, interruption and error status. The reliability design approach of FPGA was elaborated on, including the design of state machine, asynchronous clock domains, data transmission and error recovery. The unit can be used successfully in the 140Mbit/s image data transmission. For the burst error of link, the unit can recover the error data in a certain period of time, which can guarantee the validity and stability of data transmission.