According to the design requirements of LSS (Long Slit Spectrograph)

the optimization model of the LSS primary structure with the constrained conditions of the basic frequency and the objective function of total mass is established. An ACO (Ant Colony Optimization) algorithm with an improved pheromone updating rule is put forward. Based on the improved ACO algorithm and the FEA software ANSYS

a combined optimization design method is presented to solve the above structural optimization. The optimized structure obtained from the combined method has reduced about 25% in mass than the original design and is better than the optimum design obtained from the zero-order optimization method provided in the Design Opt module of ANSYS. The combined method takes advantage of the characteristics of the ACO algorithm and software ANSYS and is potential to be applied to other similar engineering structural optimization.