A personality ring-back service system used in mobile communication net includes a signaling interface unit (SIU), a service control point (SCP), a service management point (SMP) and a personality ring-back server, among which, SIU, SCP, SMP are connected by TCP / IP network, SIU is connected with a mobile net by No.7 signaling net and the personality ring-back server stores the personality ring-back sound connected with the mobile communication net by No.7 net and a session relay. The method is that a mobile user sets an unconditional call to lead forward to the ring-back service system, the SCP instructs the said server to continue call according to the stored user data, at the same time the called rings, it plays the music or other phones predetermined by the called party to the calling party and to stop playing for ordinary session between them when the called is cut in.