An operating method, a base station, and terminal of a cell of a first communication system for a handover between the first communication system and a second communication system are provided. The method includes, when a terminal initiates a handover between the first communication system and the second communication system, transmitting, by the base station, a message, requesting to measure a signal level of a downlink, to the terminal, when a signal level measured by the terminal falls below a preset threshold, requesting, by the base station, a handover to the second communication system over a core network, receiving, by the base station, a message, including radio channel parameters the that is required when the terminal accesses to the second communication system, from the second communication system, and forwarding, by the base station, the message, including the radio channel parameters of the second communication system, to the terminal.