As an ultrafiltration membrane material, novel aromatic copoly(amide-ester)(ACAE) was synthesized by low temperature solution polycondensation. This copolymer was characterized by IR, EA, X-ray, TGA thermo-grams. Membranes were cast from polymer solution consisting of ACAE, one of solvents from the group of N, N-dimeth-ylacetamide(DMAc), N-methyl2-pyrrolidone(NMP) containing lithium chloride. The permeation characteristics were investigated with regard to the effect of membrane preparation variables such as evaporation process, the composition of mixed solvents used as gelation medium and of permeation conditions such as feed concentration, operating pres-sure, molecular weight of the feed solution. As the performance test, pure water flux, solute rejection, molecular weight cut off of membranes from different preparation condition were also investigated with the aid of scanning electron mi-croscope.