In this paper,a scheme of online firmware upgrade of equipment with multiple electronic control boards is designed.By polling at certain time intervals,the electronic control boards that can be upgraded are upgraded one by one.For the electronic control boards that are located inside the air conditioning system with different functions,a single partition or dual partition OTA upgrade plan with backup areas is adopted.At the same time,measures to prevent scaling during the upgrade process are also designed to improve overall reliability.The solution not only ensures the correct and efficient firmware upgrade,but also ensures that the original firmware can be automatically restored in case of abnormal situations during the upgrade process,thereby not affecting the operation of the device.The control logic of the solution is simple and easy to implement,with a certain degree of reliability and a good user experience.