In this article, a combination of energy and force method is used for minimizing the weight of the truss structures. Genetic algorithm is employed as an optimization tool for this purpose. The main idea proposed in here is the manner in which the input variables are reduced. Using the force method is of a considerable help in handling GA for the structural optimization. In the present method, there is no need to find the inverse of matrices, and only a limited number of variables are added to GA, which is equal to the degree of static indeterminacy of the structure. The efficiency of the present approach is illustrated through several examples for different types of optimization, and the results are compared to those of different optimization techniques.