Abstract: The mechanical analysis, numerical simulation and field test were used to study the mechanism of pressure release of the pressure releasing slot and its effect. The paper established the mechanical model to study the influence of pressure releasing slot on the propagation of abutment pressure. Through the numerical simulation, the paper analyzed contrastively the change of stress and strain of the tunnel with and without pressure releasing slot. Through the field test, we verified that the pressure releasing slot could control significantly floor-heave. The results show that the pressure releasing slot cuts off the immediate bottom, changes the stress structure, and changes propagation way of the abutment pressure which is in horizontal and vertical direction. At the same time, it could absorb the extrusion deformation in horizontal direction and the floor heave volume to reduce effectively the deformation and failure of tunnels.