Wind-induced ice-shedding makes transmission-line tower system produce complex dynamic responses. This paper built a finite element model of a three-span transmission-line system. When galloping occurs in mid-span conductors, with or without ice-shedding, the dynamic responses of the transmission-line tower system were analyzed through numerical experiment, and the differences of the two load cases under different wind speeds were also studied. Besides, this paper also analyzed the dynamic characteristics of the system. In the model, the initial deformation and stress of the conductors is taken into account. The results show that the unbalanced tension of the tower head and the transverse conductor-amplitude of adjacent spans get larger with the increase of wind speed. The transverse vibration frequency of adjacent-span conductors led by ice-shedding increases dramatically, and the vertical rebound height decreases relatively. The vertical rebound height and transverse amplitude of the mid-span increase by about 73.9% and 57.7% respectively, to which special attention should be paid in the design of transmission lines.