Disclosed is a backup data deleting method, comprising: obtaining the off-line duration of a backup account number; determining whether the off-line duration is greater than a first pre-set duration; if so, sending a data deletion request to a terminal corresponding to the backup account number and receiving a deletion confirmation instruction returned by the terminal according to the data deletion request; and deleting backup data corresponding to the backup account number according to the deletion confirmation instruction. Further provided in an embodiment of the present invention are a backup data deleting device and system, a storage medium and a server.