The invention provides a route calling method, device and system, and relates to the technical field of communications. The method comprises the steps that a calling request which is launched by a CS network user, is sent by a first MGCF and corresponds to a second-level region in a first-level region is received by an I-CSCF; if the I-CSCF determines that a called number in the calling request is a non-IMS user number, the calling request is routed to a first BGCF corresponding to the first-level region to ensure that a first-level region which the called number belongs to is determined by the first BGCF according to configured phone number information of each first-level region and the calling request is routed to a second BGCF corresponding to the first-level region which the called number belongs to and is further routed to the CS network of the second-level region which the called number belongs to from the second BGCF. According to the technical scheme of the route calling method, device and system, calling between cross-first region CS network users is unclogged through an IMS network, terminal resources of traditional long-distance networks are saved, and advantages brought by IP intercommunications in IMS networks can be fully utilized.