A method and a telecommunication system for appointing a frequency assignment mode and ratio for providing a broadcast/multicast service are disclosed. The system includes at least one access terminal (AT) for receiving a 1xEV-DO service or the BCMCS through a 1xEV-DO system, a base station manager (BSM) for receiving BCMCS control information containing the FA mode and/or the BCMCS assignment ratio and transmitting the received BCMCS control information to a 1xEV-DO access network controller (ANC), and an access network including a 1xEV-DO access network transceiver subsystem (ANTS) and the 1xEV-DO access network controller for temporarily storing the received BCMCS control information and controlling a sort and/or a ratio of a message, which is transmitted to each access terminal, according to the FA mode and/or the BCMCS assignment ratio contained in the BCMCS control information.