In order to solve problems such as overlarge vibration around the first critical speed of rotating machinery and high failure rate, a rotor bench is established to study the rotor vibration suppression effect by the designed magneto-rheological dampers. Rotor faults such as unbalance, rub and misalignment are imitated at the bench, and experimental research is done to study the rotor vibration suppression effect of the damper without stop. The results show that the dampers can suppress rotor vibration caused by those faults, by reducing the vibration around the first critical speed by 60% and eliminating the amplitude at high frequency caused by rub and misalignment.