The invention discloses a method for realizing ONLY resonance service. A calling user makes a call to an ONLY resonance user, after receiving the call request, an ONLY application server (AS) carries out media negotiation with one of the resonance numbers contracted with the ONLY resonance user; if the media negotiation is successful, the calls to the other resonance numbers contracted with the ONLY resonance user are made; if the media negotiation fails, the other resonance number is selected for carrying out media negotiation, until the calling user and a resonance number carry out media negotiation successfully, later, the calls to the other resonance numbers contracted with the ONLY user are made. By using the method for realizing ONLY resonance service, after the ONLY AS and one of the resonance numbers of the ONLY user carry out media negotiation successfully, then the calls are made to the other ONLY resonance numbers contracted with the ONLY user, and the calls to the other ONLY resonance numbers can be guaranteed to be successful.