In this study, a partially earth-anchored cable system is studied in order to reduce the dynamic wind response of cable-stayed bridges. The employment of earth-anchored cables changes the dynamic characteristics of cable-stayed bridges under wind loads. In order to estimate the changes in the member forces, the spectral analysis for wind buffeting loads are performed and the peak responses are evaluated using 3-D finite element models of the three-span cable-stayed bridges with the partially earth-anchored cable system and with the self-anchored cable system, respectively. Comparing the results for the two different models, it is found that the earth-anchored cables affect longitudinal and vertical modes of the bridge. The changes of the natural frequencies for the longitudinal modes remarkably decrease the peak bending moment in the pylon and the movements at the expansion joints. The small changes of the natural frequencies for the vertical modes slightly increase bending moments and deflections in the girder. The original effects of the partially earth-anchored cable system are also shown under wind loads; the decrement of girder axial forces and bearing uplifting forces, and the increment of cable forces in the earth-anchored cables.