Abstract: A method for protecting a system from being powered off abnormally during an upgrade, which is applied to a system upgrade of a terminal device, comprises: acquiring a startup offset value of one of the plurality of storage partitions; when the startup offset value is the first offset value, starting the first system image file; acquiring an upgrade file, performing an upgrade operation on the second system image file in the current storage partition by using the acquired upgrade file, and setting the startup offset value as the second offset value when the upgrade is successfully completed; and continuing to perform the upgrade operation on the first system image file, and setting the startup offset value as the first offset value when the upgrade is successfully completed. The terminal device is powered off when upgrade operation is performed so that the system of the terminal device cannot be started normally.