With the rapid development of technology, FPGA has been widely used in multiple fields due to its flexibility and high performance. Faced with constantly changing application requirements, the online upgrade technology of FPGA has become one of the key challenges. A FPGA online upgrade optimization design based on RS422 interface was adopted, fully utilizing the long-distance transmission and anti-interference advantages of RS422, and achieving stable communication between the upper computer and FPGA development board. The control instructions and configuration data are received through the RS422 communication module, and the FPGA control module is responsible for parsing the instructions and performing operations such as erasing and writing to FLASH to ensure smooth firmware updates. By utilizing the ICAP module and Multiboot function, dynamic reconfiguration has been designed and implemented, enabling recovery through Fallback mode even in the event of unexpected situations during the upgrade process. In order to further improve the reliability of data transmission, a technical solution combining RS encoding and CRC check has been introduced. The combination of the two not only improves the accuracy of data transmission, but also enhances the system's error correction capability, effectively responding to sudden errors and noise interference, ensuring the safety and stability of FPGA online upgrade process.