In this paper, we propose an effective and accurate method for optimizing space steel frames with semi-rigid joints using practical advanced analysis (PM) and micro-genetic algorithm (mu GA). The PM method using the beam-column approach is applied for capturing the second-order effects and the inelastic behavior of systems, while the zero-length element model is employed for estimating nonlinear behavior of semi-rigid joints. mu GA is utilized for finding the global optimal solution, and OpenMP is employed to perform parallel computing in order to efficiently reduce computational time. In this study, unlike many previous researches, not only cross-sectional areas of beam and column members but also semi-rigid connection types are variables of the optimization. The results of some steel frame examples prove that the proposed method is computationally efficient and reliable. (C) 2016 Elsevier Ltd. All rights reserved.