A mixed ionic and electronic conducting (MIEC) membrane provides an alternative to the palladium alloy membrane for water gas shift membrane reactor. It exhibits much better sulfur resistance performance than the palladium alloy membrane. In this paper, the thermodynamic performance of the integrated gasification combined cycle (IGCC) system with MIEC membrane reactor is predicted for the first time. The effects of reactor operation parameters on system flowsheet and performance are investigated and illustrated by sensitive analysis. When the reactor operation temperature is 900 degrees C and the H2O decomposition ratio is 0.5, the system net efficiency is about 38.90%, which is 2.6% points higher than that of the IGCC with Selexol. The system net efficiency increases with the decrease of operation temperature. With the net efficiency of the conventional system as the reference, the minimum H2O decomposition ratios at different operating temperatures are provided. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.