Novel copoly (phthalazinone ether sulfone) (PPBES) UF membranes with excellent performance were prepared with phase inversion method. The types of solvent, the effects of PPBES concentration, EGME concentration and coagulation temperature on the morphologies and performances of UF membrane were investigated in detail. The structures of the membrane were characterized by scanning electron microscope (SEM). With the increase of EGME concentration in the casting solution, the morphologies of the UF membrane changed from finger-like structure to sponge-like structure. The thermal stability of the PPBES UF membranes prepared in this work was investigated with Sulfur Black B dye solution. When the temperature of feed solution was raised from 20 to 95 degrees C, the permeation flux increased more than three times while the rejection change was not observed. (C) 2010 Published by Elsevier B.V.