Out-of-round (OOR) wheel often happens to trains, which can cause abnormal vibration. To develop effective countermeasures to minimize the abnormal vibration, it is necessary to study how the wheel OOR wear affects the vehicle vibration. This paper performs an experimental study on the abnormal vibration characteristics of metro trains with out-of-round wheels. The vibration characteristics is identified by the general survey of wheel roughness from special tests. The statistic wheel wear values of all the vehicles in an operating metro lines are studied to investigate the relationship between the wheel wear and the operating mileage. Several re-profiling strategies are implemented to eliminate the abnormal vibration caused by wheel OOR. The results show that the root cause of the abnormal vibration and deterioration of ride comfort is the car-body flexible resonance excited by the wheel OOR wear. Wheel re-profiling is the most effective measure for reducing the vehicle abnormal vibration. By re-profiling all the wheels of a tested metro vehicle, the ride comfort can be improved by 35% ∼ 40% and the axle-box acceleration can be reduced by 40%.