The sensitivity of the dynamic wind-induced deflection responses of the insulator string can show the relationship between the deflection amplitude and design parameters，which is conducive to the understanding and use of designer. In order to explore the sensitivity characteristics of the dynamic wind-induced deflection response of insulator strings，the equivalent model of conductor that can fully characterize the wind-induced deflection of overhead lines is proposed by the principle of constant natural frequency，a two-degree-of-freedom dynamic model for the coupled wind-induced deflection of the insulator string and the overhead conductor is established. Based on the amplitude-frequency characteristic curve and the fluctuating wind speed spectrum，the mean square value of wind-induced deflection response is used to analyze the sensitivity of the wind-induced deflection of insulator string to the overhead lines structure and wind speed，and an expression for the sensitive wind speed of the dynamic wind-induced deflection response is proposed. The result shows that the mean square value of the wind-induced deflection of the insulator string is proportional to the vertical horizontal ratio of the overhead lines. When the average wind speed is the sensitive wind speed，the amplitude of the wind-induced swing of the insulator string reaches the maximum value. In the design of overhead lines，the lines structure should be reasonably selected so that the sensitive wind speed of the insulator string to avoid the local maximum wind speed，thereby reducing the possibility of wind-induced deflection flashover on the lines.