In order to optimize the location and quantity of viscous dampers on the large-span truss structure, the maximum value is obtained by summing the percentage of modal strain energy of replacement bars, and thus taken as the objective function. The peak values of node displacement, acceleration and element stress are regarded as the optimization control index. In addition, Matlab is adopted to verify an adaptive genetic algorithm optimization program. Based on the optimization result, the seismic control effect of the optimized truss structure under the frequent and rare seismic is compared through ANSYS analysis. The results show that the optimized scheme of damper has superior damping effect, which can obviously improve the stress situation of structure. Therefore, the best optimization scheme is obtained and the rules for optimal location of viscous dampers in large-span truss structures are summarized through taking safety and economy into account, which is of reference significance for the actual engineering damping design.