A subscription update method, device, and system, where the method is performed by a first event notification network element and includes: determining that a notification condition of a first subscription event of a first terminal is met; obtaining first callback address information of a target subscription network element; and sending a first message to the target subscription network element based on the first callback address information, where the first message carries an identifier of the first terminal and a first event notification of the first subscription event, and the identifier of the first terminal is used to correlate the first event notification with the first terminal.