Abstract: Since the metro FAO system that adopted GoA4 cancelled the setting of train driver, in some abnormal scenarios or degrade cases, the train is forced to stop in a certain section, that makes it difficult for the rescue members to work，resulting in time wasting and even serious impact on train operation safety. In this paper, according to the specific fault, a corresponding fault softening technology is proposed. In case of the AFO system failure, part of the system functions will be retained and the train stopping between stations will be avoided, and the goals of minimum impact on the operation by reducing the rescue difficulties and serving the passengers in abnormal scenarios or degrade cases will be achieved.