Abstract: On the basis of full-stress design, an imitative full-stress design method is proposed for structural optimum design with discrete variables. The structural optimum design with discrete variables under stress and section size constraints is performed using this method. Through introducing an imitative full-stress design operator in the genetic algorithm, a hybrid genetic algorithm for structural optimization with discrete variables is presented in this paper. Numerical results show that the hybrid genetic algorithm is efficient for structural optimum design with discrete variables.