Abstract: This paper presents a genetic algorithm (GA) for optimizing truss structural system with discrete design variables. It differs from existing mathematical programming methods in that the GA uses a population of initial points in contrast to the single-point approach by the traditional ones. The optimal solution by GA is no longer dependent on initial search values, and will guarantee a global optimum. Derivative calculation is not necessary and computer program is simple. Genetic algorithm is best suited for structural optimizations which have discrete variables.