In order to acquire a high quality of living environment, it is necessary to investigate the subjects of floor impact sound insulation. According to the characteristics of optimization design method and restricted optimization math model, the sound transmission between floor and adjacent room down through floating floor has been modeled in a finite-element method. Floating floor structure are studied to realize the design optimization when the room average sound pressures are selected as objective function. Predicted results show that when keep the whole thickness of floating floor fixed, result of dynamics optimization design can reduce room average sound pressure effectively. And when keep the whole thickness of floating floor unfixed, optimization results have been gotten on the total thickness of floor layer and resilient interlayer of the floating floor, and the average sound-pressure in room is lower than original one availably.