A composite ultrasonic energy transmission system with the serial structure horn is presented for the wire bonding application. Compared with the conventional parallel structures, this one can greatly reduce the structural coupling effect. Energy density formulation is deducted theoretically. Through the vibration characteristic analysis and FEA verification, it is proved that this serial structure can obviously increase the composite output amplitude of the ultrasonic horn and the ultrasonic energy density so that it will shorten the bonding time and improve the bonding efficiency.