The sulfonated-polyethersulfone (SPES)/nano-TiO2 composite ultrafiltration (UF) membranes were prepared by phase inversion method with nano-TiO2 as additive. The TiO2 self-assembly on the SPES membrane was confirmed by FT-IR and the isoelectric point’s analysis (IEPs). The electrokinetic phenomena of composite membrane in the different single electrolyte solution were investigated by the streaming potential method. The results showed that the IEP of the SPES-UF membrane modified by nano-TiO2 shifts from 3.5 to 2.9, and the composite membrane shows a stronger electronegativity, which indicates the antifouling performance improvement of the SPES-UF membrane modified by nano-TiO2. The valences of the cations and anions have an important influence on the streaming potential of the composite UF membrane.