Soluble copolysulfoneimides were synthesized by a thermal two-step method. Bis[4-(3-aminophenoxy)phenyl] sulfone (BAPS-m) and 3,3'-diaminodiphenyl sulfone (3,3'-DDS) as diamines were used. PMDA, DSDA and ODPA were used as dianhydrides. In order to reduce the amount of BAPS-m, 3,3'-DDS was added, as much as possible. Ultrafiltration (UF) membrane with the polymer was prepared by the phase inversion method. Various solvent (water, alcohols, acetone and hexane) fluxes were measured. Phospholipid could be rejected above 90%. The soybean oil micelles could be concentrated to volume concentration ratio (VCR) of 10. Several effects like feed temperature, stirring speed and feed solid concentration on micelle flux were also investigated. Resistance values of membrane, concentration polarization and fouling were measured.