A new method of vibration suppression, interior inlay viscous fluid unit (IVFU), has been proposed and investigated in this paper. Experimental results show the inherent characteristics of interior inlaid fluid subsystem in suppressing the plate vibration. A numerical simulation is carried out using software FLUENT. The original liquid-solid coupling model is rationally simplified to an approximate hydrokinetic model by constructing the fluid dynamic boundary conditions. A criterion of energy dissipation is proposed. Simulation results show that under the first principal vibration, the damping effect of 1/2 volume water is better than that of 2/3 volume, and under the second principal vibration, the latter behaves a self-adaptive characteristic more than the former. Simulation results clearly illustrate the inherent mechanism of suppressing vibration and the characteristic of fluid movement in closed cavity on different situations.