The DSP online upgrade requires multiple power outage and restarts, and in the face of unexpected situations may lead to upgrade failure and cannot return to the original version. The DSP online upgrade method is optimized. The entire upgrade processes don’t require power outage and restarts by joining the external watchdog.The AB zone mode is introduced in the FLASH partition, and the online seamless upgrade of DSP is realized to improve the fault tolerance of the online upgrade. The above optimization is fully verified by experiments, experimental results show that the online seamless upgrade method is easy to operate and has fault tolerance, which can be widely used in the online upgrade of the embedded system.