Abstract: In order to analyze the isolation effectiveness of in-filled trench to the ground vibration caused by subway operation, a coupling model, which is divided into five parts including moving train, track structure, lining, ground and in-filled trench, is established. The train load is simulated by a set of constant loads consistent with the spatial distribution of train axles. The rails and floating plates are simplified as the infinite Euler beams. The lining and ground are simulated as the homogeneous elastic media. The theoretical model is coupled by the continuous conditions for the stresses and displacements between the rail and the lining invert and those between the lining and the ground. The concrete in-filled trench is modelled as the heterogeneous medium in the ground. The interface between the in-filled trench and the ground is treated by the common node method and solved in the wave number domain. Finally, the three-dimensional dynamic response in the time-space domain is obtained by the fast inverse Fourier transform (IFFT). The vibration-isolation effectiveness of the filled trench under different train speeds, in-filled trench depths, trench widths and tunnel depths is calculated and analyzed. The results show that its vibration-isolation effectiveness is improved with the increase of the in-filled trench depth, but when the depth of the in-filled trench exceeds a certain depth, the improvement rate of the vibration-isolation effectiveness slows down. With the increase of the distance between the in-filled trench and the subway, the isolation effectiveness decreases in the area before the in-filled trench and increases in the area after the in-filled trench. With the increase of train speed, the vibration-isolation effectiveness becomes better.