The local vibration of a bridge under moving train is the source of low frequency noise radiated from the structure. Local vibration of bridges has not been widely studied compared to global vibration that leads to serviceability and safety problems. The local vibration of an urban rail transit U-shaped girder is simulated with the proposed mode superposition based train-track-bridge dynamic interaction model. The computed local acceleration responses under various train speeds are then verified by those obtained from field test, in terms of time-histories, spectra, peak-to-peak values and root mean square (RMS) values. It is founded that the main frequencies of the local acceleration of this girder are below 100 Hz. The proposed method and the computed local vibration could be further applied to predict the bridge-borne noise.