In view of the abnormal vibration of a carriage floor in the delivery process of a metro vehicle, a large number of vibration tests and analysis were carried out to find the source of the abnormal vibration and eliminate the possibility of the transformer box and floor resonance. Through the analysis of the vibration transmission characteristics, it was determined that the floor vibration anomaly was caused by the local resonance of the car body beam near 98 Hz, and the solution was put forward. Finally, the floor vibration was reduced by 34% after optimizing the isolation layer below the floor.