Abstract: Wind turbines are usually installed on-site where wind-introduced vibration may result in significant difficulty in the installation of the generator blades because of the large displacement at the top of the tower. To reduce such a big displacement response, a two-way rail type tuned mass damper (TMD) is developed in this study which is featured with a frequency-adjustable mechanism. This paper reports the selection of primary parameters of the TMD, the numerical simulation and an experiment test. The primary parameters are first selected based on the structural dynamics, from which the mass, stiffness and damping ratio can be determined. Finite element analyses are conducted to further consider the contribution from higher vibration modes. A scaled model of the tower and the TMD are fabricated and tested to demonstrate the effectiveness of the TMD.