The invention provides a call routing method and system for a number one service in an IP (Internet Protocol) multimedia subsystem network, belonging to the technical field of communication. The method comprises the following steps of: obtaining state information of a first called terminal and/or a second called terminal, wherein the first called terminal and the second called terminal are pre-bound by a called number; and the called number orders the number one service in the IP multimedia subsystem network; receiving a call request sent to the called number; and adjusting call routing of the first called terminal and/or the second called terminal according to the state information. According to the call routing method and system disclosed by the invention, the occupation on network resources can be effectively reduced when route calling is carried out.