Geotextile bag buried in subgrade can improve the bearing capacity of subgrade and also reduce or isolate vibrations. A series of horizontal cyclic shear tests are carried out to investigate the dynamic characters of piled geotextile bag. The test results indicate that geotextile bag is excellent materials for base vibration reduction and isolation as it has variable horizontal stiffness and large damping ratio. The damping ratio of geotextile bag decreases with increasing of vertical pressure, and increases with the increasing of maximum shear strain. Besides, the discrete element analysis is carried out on a geotextile bag under cyclic loading. The contact between soil particles in geotextile bag is modeled as a spring-dashpot system. The geotextile bag is modeled as coating of small particles with tension. The contact between the small particles in coating is also spring-dashpot system which has no tangential contact but only normal contact, and can only carry tension stress. The simulation results illustrate that the vibration reduction of geotextile bag is due to the energy dissipation mainly resulting from frictional and viscous forces among soil particles and the tension of bag. Moreover, in-situ tests are performed on a trench built with geotextile bag to validate the vibration reduction and isolation effect of geotextile bag.