A method for managing user information in an instant messaging system, the instant messaging system comprising a plurality of access servers, wherein an access server is used for managing information of users and contacts of users logged into the access server, the method comprising: obtaining and storing, by a first access server of the plurality of access servers, information of contacts of a user who is logged in to the first access server, wherein a reverse buddy table stored on the first access server includes identifiers of reverse buddies of the user, wherein a reverse buddy refers to another user that has added the user as buddy; in response to a determination, by the first access server, that the user exists in the reverse buddy table: send a notification, by the first access server, to notify at least one other access server of the plurality of access servers of user information of the user; and store, by the at least one other access server which receives the notification, the user information of the user upon determining that a contact of the user exists therein, wherein the at least one other access server is configured to: in response to a determination that the user exists in a reverse buddy table of the at least one other access server, change, in the reverse buddy table of the at least one other access server, a corresponding position information of the server of the user to indicate the first access server; and performing a search locally in the first access server or in the at least one other access server when the first access server needs to obtain the information of the contacts of the user. obtaining and storing, by a first access server of the plurality of access servers, information of contacts of a user who is logged in to the first access server, wherein a reverse buddy table stored on the first access server includes identifiers of reverse buddies of the user, wherein a reverse buddy refers to another user that has added the user as buddy; in response to a determination, by the first access server, that the user exists in the reverse buddy table: send a notification, by the first access server, to notify at least one other access server of the plurality of access servers of user information of the user; and store, by the at least one other access server which receives the notification, the user information of the user upon determining that a contact of the user exists therein, wherein the at least one other access server is configured to: in response to a determination that the user exists in a reverse buddy table of the at least one other access server, change, in the reverse buddy table of the at least one other access server, a corresponding position information of the server of the user to indicate the first access server; and send a notification, by the first access server, to notify at least one other access server of the plurality of access servers of user information of the user; and store, by the at least one other access server which receives the notification, the user information of the user upon determining that a contact of the user exists therein, wherein the at least one other access server is configured to: in response to a determination that the user exists in a reverse buddy table of the at least one other access server, change, in the reverse buddy table of the at least one other access server, a corresponding position information of the server of the user to indicate the first access server; and performing a search locally in the first access server or in the at least one other access server when the first access server needs to obtain the information of the contacts of the user.