This paper verified the effectiveness of nonlinear finite element model according to the tested displacement of double loop line tower for UHV transmission line which was under the most unfavorable load combination. Then, the implicit nonlinear dynamic analysis was carried out on the strain section of transmission line system in the most unfavorable position. Through examining the dynamic effect of transmission tower when 1 to 4 wires were cut off, it can be confirmed that the breaking of all four wires and the breaking of the uppermost wire has the greatest influence on the dynamic effect of the transmission tower in the broken area. The influence of the lateral stiffness, span, line angle and elevation on the suspension points in broken area under the dynamic effect of the transmission tower was analyzed at the same time. The results show that the increase rate of the dynamic effect of the line tower in the broken area increases gradually with the decrease of K (the relative lateral stiffness) when the stiffness of the line tower in the unbroken area is smaller than that of the broken area (K<1). However, in the case of K>1, the increase rate of the dynamic effect of the line tower in the broken area decreases gradually with the increase of K. Further, the dynamic effect of the transmission line tower on the disconnected side increases significantly in a geometrical relationship when the span distance extends to the unbroken area, but the extension of the span distance is linearly and positively correlated with the dynamic effect of the break-line transmission tower. When the turn angle of line or the elevation angle of suspension points is ±5° or ±7°, the maximum dynamic displacement value and the maximum displacement value in the stability of the broke-line transmission tower both exceed 1.822 m.