This paper introduces a method for remote firmware upgrade of FPGA based on the 1553B bus, and verifies the feasibility of this method through practical operations. During FPGA software upgrades, issues such as slow upgrade speed, inability to read back data, requirement for product disassembly, and inconvenience in solidification exist. By adopting technologies including the 1553B communication protocol and timing control technology, single-FLASH dual-region storage technology, cyclic redundancy check (CRC) algorithm, and reliable handshaking protocol technology between upper and lower computers, an online upgrade system with software erasure/writing, intelligent verification, and data read-back functions is designed and implemented.