The invention discloses a method and a system for restoring an online charging state of a user. The method comprises the steps of building a mobile management entity (MME) interface information management library associated with the user; transmitting subscription information of the user to a home subscriber server (HSS); querying MME information associated with the user in the HSS; determining an MME interface associated with the user according to the MME information, returned from the HSS and associated with the user, and the MME interface information management library; and transmitting a request of restoring the online charging state of the user to the MME associated with the user through the MME interface associated with the user.