A user locating system, method and server in a Packet-based network. A plurality of management regions divided by terrains are included, and each of the management regions includes: an address management server adapted to collect and bind communication addresses and user identifiers of all network users in the management region, and to send information of the binding to a region locating server in the present management region; and a region locating server adapted to store and update the information of the binding of the user identifiers and the communication addresses of all the network users in the present management region, to send the information of the binding to a inquirer dependent upon a received inquiry request, and to send information of binding of a user identifier and a communication address found not belonging to the present management region to a home management region of the user.