The ratio of every coefficient of nonlinear stiffness terms to coefficient of linear stiffness term at different horizontal tension is analysed，which in the first three vibration mode．Through discussion relationship between amplitude of vibration and horizontal tension，linear restoring force as well as nonlinear restoring force，the main factors that influence strong or weak geometric nonlinearity of icing conductor system were determined．On the basis，the steady state amplitudes and vibration frequency of system were calculated with undetermined natural frequency method，numerical results show the amplitudes of vibration increase with wind velocity increase in each vibration mode，and frequency of each order vibration mode would deviate from original fundamental frequency while system was subjected effect of geometric strong nonlinearity．The analysis results of conventional normal form was difficult to meet accuracy requirements of model analysis，and the analysis results in this paper could relatively accurately grasp vibration characteristics of model．