To reduce the vibration hazard of adjacent buildings caused by metro operations, a vibration reduction method of thickening the base floor of raft foundation buildings was proposed, and the vibration reduction effect of the thickened floor was studied. The three-dimensional model of “tunnel-soil-building” was established, and the model and vibration source load were verified using measured data and empirical formula. The vibration reduction effect of the thickened base floor of raft foundation building under the conditions of ordinary track bed, elastic long sleeper track bed, and steel spring floating slab track bed was examined. The influence of the horizontal distance between the building center and the metro tunnel center on the vibration reduction effect of the thickened floor was analyzed. Results showed that the thickened raft foundation effectively consumed the vibration energy caused by metro, reducing the vibration response of adjacent buildings. When the damping track bed was employed in the metro line, the damping effect was weakened to a certain extent. The vibration reduction effect of the thickened base floor was related to the horizontal distance between the building and the tunnel centerline. The closer the distance was, the better the vibration reduction effect was. Finally, a prediction method for quickly calculating the vibration reduction effect of the thickened base floor of raft foundation building was proposed, which can provide a reference for practical engineering.