In this paper， an isolated structure system with lateral fluid viscous damper is proposed to control horizontal acceleration， horizontal displacement and swaying response without affecting vertical isolation effect. Based on the deformation analysis of isolation layer and lateral damping system， a rigid body dynamic theoretical model is established considering the coupling effect of the translational and swaying of isolation layer and the coordinated rotation deformation of lateral fluid viscous damper. Based on RG1.60 spectrum，30 input seismic signals are selected to carry out parameter analysis. The arrangement of damper （parameter fd）， ratio of damping force to reaction force of isolation layer （parameter fc） and the damping exponent （parameter fα） are chosen as three main parameters， whose sensitivity is discussed through non-linear dynamic time-history method. It is found that the optimal ratio of damping force to reaction force of isolation layer is 10-20%. Under the optimal parameters， the horizontal acceleration displacement can be reduced by 20% and 40% respectively， and the maximum rocking response can be reduced by 70%. Optimal damping parameters are selected to complete the case study. The seismic response including rocking response， acceleration and displacement of isolation layer are reduced. The numerical simulation results of the case study are consistent with the parameter analysis and are consistent with theoretical analysis.