Abstract: The common finite element analysis software ANSYS was adopted as the running environment. Member cross section areas of the lattice grid structure were taken as the discrete design variables. The total weight was considered as the objective function. The restrain conditions such as strength, rigidity, stability and cross section dimensions were considered. The one-dimensional search method and the modified stress ratio method were selected as the optimization method. Optimization of the lattice grid structure was conducted. The calculated results show that the optimal method has easy principle and big convergence rate. It can reduce the cost of a project on the base of guaranteeing safety, and can get a better optimal result.