Abstract: Traffic loading is usually simulated by single cyclic deviator stress. However, the vertical normal stress and horizontal stress acting on the soil elements are all varied cyclically under the traffic loading. Nevertheless, part of the subgrade soil is overconsolidated, rather than normally-consolidated. There are few researches on the development of damping ratio of soft clay under the traffic loading. Hence, a series of cyclic triaxial tests with cyclic confining pressure are conducted on the overconsolidated clay under undrained conditions, and the effects of cyclic confining pressures and overconsolidated ratios on the development of damping ratio are investigated. It is observed that the relationship between the normalized damping ratio and the cumulative axial strain are similar under different test conditions, in which the normalized damping ratio degrades with the increasing cumulative axial strain. Besides that, the overconsolidated ratios and cyclic confining pressures have significant effects on the development of damping ratio: the damping ratio decreases with the increase of the overconsolidated ratio and cyclic confining pressure. Based on that, an empirical formula as a function of the cyclic confining pressure and overconsolidated ratio is proposed to predict the damping ratio. The above results can deepen the understanding of damping ratio of the overconsolidated soft clay under the traffic loading, and provide experimental basis for the dynamic analysis of soils under the traffic loading.