Membrane plasma fractionation is an important part of double filtration plasmapheresis. We evaluated a newly developed polyethersulfone (PES) hollow-fiber plasma fractionation membrane, using 3 parameters: abnormal protein ratio (APRR), different protein ratio (DPR), and plasma filtration efficiency, except sieving coefficients. The APRR of the fractionation membrane was over 0.90, and the DPR changed after the plasma fractionation. We also compared the sieving coefficients of the PES hollow membrane with some commercial plasma fractionation membranes. The data were significant for the clinical use of the PES hollow-fiber fractionation membrane.