An interactive short message service (SMS) system, which can offer an interactive short message service even in a private wireless network, and a routing method therefor are disclosed. The interactive short message service system in a private wireless network, which is interworked with a public land mobile network (PLMN) and provides a public mobile communication service and a private wireless network service to a mobile station (MS), includes a private base station controller (pBSC) for performing routing to the private wireless network through a private mobile switching center (pMSC), or routing to the public land mobile network through a base station controller (BSC) of the public land mobile network, according to a destination address of an initial originating message when there is a request for an interactive short message service through a private base transceiver station (pBTS) from the mobile station, a private short message service center (pSMSC) connected to the private mobile switching center, and an interactive short message service server for communicating with the private short message service center (pSMSC) and providing the interactive short message service to the mobile station according to routing performed by the private base station controller (pBSC) to the private wireless network.