Zwitterionic (ZI) membranes are well-known for their high resistance to protein fouling during ultrafiltration (UF). In this work, zwitterionic chitosan (ZICS) was firstly obtained by a Schiff-base formation and a sulfonation reaction. Then a series of zwitterionic organic-inorganic hybrid ultrafiltration membranes were prepared through linking ZICS with poly vinyl alcohol (PVA) using tetraethyl orthosilicate as a bridge, where the density of zwitterionic groups in the membranes was adjusted by varying the dosage of zwitterionic chitosan. The prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and the measurements of water contact angle and zeta-potential of membrane surface. The ultrafiltration performance was examined using the separation of bovine serum albumin (BSA) and lysozyme (LYZ) as a model system. The results show that, zwitterionic chitosan-silica-PVA hybrid membranes can possess desirable porosity, hydrophilicity, permeability, antifouling capacity and selectivity which can be adjusted by the fraction of ZICS in membranes. (C) 2015 Elsevier B.V. All rights reserved.