Abstract: Phenomenon about wind-rain-induced vibration on cable-stayed bridges has attracted more attention worldwide in recent decade, and mitigating stay cables vibration by means of magneto-rheological (MR) damper is taken as a new exploration. In this paper, numerical simulations of a full-scale stay cable incorporated with MR damper are performed with Bingham model, and relationships of modal damping ratio versus attachment location of damper, ambient exciting force and voltage input to damper are acquired. A full-scale test of mitigating vibration using MR damper on Dongting Lake Bridge of Hunan province in China is reported, and test data are in good agreement with numerical results, indicating that the numerical model and the simulation method are reliable and effective. Mitigating vibration performance of MR damper is also simulated, and the results show that MR damper has a good mitigating effect. This has been verified by the acceleration responses measured when wind-rain induced vibration occurs. The present work will supply a guidance on the use of MR damper in cable-stayed bridges.