Abstract: The discrete model of reinforced concrete structure considers the actual distribution of rebars, and with high accuracy, but the modeling process is complex. A kind of simplified modeling method is adopted to establish the finite element reinforced concrete model of opto-mechanical structure of ICF. This method is a kind of integrated modeling method with the equivalent modal feature of discrete model, by which concrete and rebar are considered as a kind of equivalent material. For typical combined structure, equivalent component models are obtained, and these equivalent models are assembled as a general structure. The numerical simulation results indicate that, under the same excitation, the response of discrete model and equivalent model is rather close, and the size of equivalent model is rather smaller than that of discrete model, and the effectiveness of equivalent modeling method is validated. At last, this equivalent modeling method is applied in opto-mechanical structure of the ICF facility SG Ⅲ, the random response of target ball is calculated under tested base excitation, and the simulation result and test data match well. The equivalent modeling method could be used in further stability analysis of giant opto-mechanical structures.