A method based on gust loading factor (GLF) for evaluating along-wind response of a wind turbine sys-tem was proposed. The approach presented was different from conventional GLF methods as the GLF contained contribu-tions from two resonant modes, mainly due to blade/tower interaction effects. The wind turbine system model considered here contained two interconnected flexible subsystems, the tower and the blade rotor ones. Each component was initially modeled as a single degree-of-freedom (DOF) system, and these were coupled together to form a two DOF reduced order model of the coupled blade/tower system. Thus, the resonant components of the response contained energy output from the two modes of the coupled system. The GLFs were obtained for both tower tip displacement and base bending moment through numerical integration, and a closed form souhion to the former was also obtained. A series of numerical examples were given to investigate the magnitude of GLFs obtained for the two DOF assembly which allowed blade/tower interaction,and these were compared with GLF values obtained from a single DOF model which ignored blade/tower interaction.