Microporous carbon membranes (MCM) were prepared from sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) through stabilization and pyrolysis processes. The effects of sulfonation degree (SD) of SPPESK and the stabilization temperature on the structure and gas permeation of MCM were investigated. The thermal decomposition behavior of SPPESK was studied by thermogravimetric analysis-mass spectrometry. The evolution of functional groups on membrane surface was detected by Fourier transform infrared spectroscopy during heat treatment. The resultant MCM was characterized by X-ray diffraction, Raman spectroscopy, nitrogen adsorption technique and pure gas permeation test (including the gases of H(2), CO(2), O(2), and N(2)), respectively. The results have shown that the removal of sulfonic acid groups in SPPESK leads to a weight loss stage in the temperature range of 250-450 degrees C. The surface area, maximum pore volume, and gas permeability of MCM increase with the SD increasing from 59 to 75%, together with the reduction of selectivity. Similarly, the gas permeability of MCM also increases with elevating the stabilization temperature from 350 to 400 degrees C at the loss of selectivity. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 1190-1197, 2011