A subscription method and device based upon the session initiation protocol are disclosed, such that a function of permanent subscription and temporary subscription is achieved, and a time at which a notification is sent can be customized. In the present invention, a mechanism of permanent subscription and temporary subscription is introduced. Upon reception of a SUBSCRIBE message, a notifier sets a temporary subscription flag or a permanent subscription flag for a subscriber according to an identifier carried in the message or service characteristic corresponding to a subscribed event. In the case of the permanent subscription flag, a NOTIFY message from the notifier is continuously sent until the subscriber or the system revokes subscription, and in the case of the temporary subscription flag, the notifier no longer sends a NOTIFY message upon finishing of a subscribed service. The subscriber may also carry a parameter indicative of a start time at which subscription gets validated and/or a parameter indicative of a time at which a notification is sent in the SUBSCRIBE message sent to the notifier. The notifier parses the message and sends the NOTIFY message to the subscriber when the start time at which subscription gets validated is reached and/or according to the time at which a notification is sent.