To study the dynamic response of the tunnel and soil when the subway train passes the transition section of the floating slab track， this paper proposed a semi-analytical ring layered element for the efficient calculation of the tunnel-saturated soil vibration in time domain. Taking into consideration of the train-track model， the coupled dynamic model of the train-floating slab track transition section-tunnel-soil system was finally established. The effects of the parameters of the floating slab transition section （i.e.， the length and the stiffness of the steel spring） on the tunnel acceleration， soil normal stress and pore water pressure were studied. The results show that the parameter design of the floating slab track transition section needs to focus the dynamic responses at the two positions of sudden changes in stiffness of the transition section. The scheme of the gradient in steel spring stiffness can reduce the three evaluation indexes of the dynamic response by 60%， 15% and 25% respectively.