Abstract: This paper aims to explore the dynamic wind-induced deflection of suspension insulator string under fluctuating wind and its characteristics, to make up for the deficiency of its research mainly focuses on static formula calculation and finite element analysis, and to provide theoretical reference for design of practical projects and prevention of wind-induced deflection. The response of conductor under fluctuating wind is assumed to be small deformation and the effects of its vibration mode and continuous spans are ignored. By analyzing the force state of insulator string and conductors in the transmission line without height difference, inertial force is introduced on the basis of static formula, and the aerodynamic damping effect is considered. According to the d'Alembert's principle, a dynamic equation of wind-induced deflection of suspension insulator string is established and it can be solved by the fourth-order Runge-Kutta method. Through case analysis, it is found that this theoretical model can be adopted to effectively calculate the time history of insulator string's wind-induced deflection, and the range of wind-induced deflection angle floating around its mean value decreases when wind speed increases. Besides, the dynamic amplification factor of fluctuating wind on the target insulator string's wind-induced deflection angle is mainly between 1.05 and 1.45, so the dynamic amplification effect cannot be ignored and it will decrease with the increase of wind speed.