In this study, the operating conditions of a thermally coupled membrane reactor (TCMR) in gas-to-liquid (GTL) technology are optimized via differential evolution (DE) method to maximize the hydrogen mole fraction in the endothermic side as well as the gasoline yield in the exothermic side. TCMR is designed as a double pipe reactor where highly exothermic Fischer-Tropsch synthesis (FTS) reactions in the exothermic side are coupled with decalin dehydrogenation reaction in the endothermic side. The minimum required hydrogen molar flow rate in the recycled stream is optimized to compensate a hydrogen lack at the end of the reactor in the exothermic side. The optimization results show 14.28% increase in the gasoline yield in optimized TCMR compared with conventional tubular reactor (CR). Moreover, 81.49% hydrogen is produced in the endothermic side and about 1% hydrogen is recycled to the exothermic side for utilization in FTS reactions in optimized TCMR. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.