Porous membranes were prepared through thermally induced phase separation (TIPS) of polyphenylene sulfide (PPS)/diphenyl ketone mixtures. The phase diagram of PPS/diphenyl ketone system was drawn by cloud point temperature and dynamic crystallization temperature. SEM images and porosity were used to characterize PPS membrane structures. According to the analysis of phase diagram, three main effecting factors including polymer concentration, cooling rate, and nucleating agent could control the pore structure and pore size for the preparation of symmetry and asymmetry membranes. The experimental results are coincident with the theory prediction. (c) 2007 Wiley Periodicals, Inc.