Poly(vinyl chloride) (PVC) ultrafiltration membranes with improved antifouling properties were prepared by using a non-solvent-induced phase inversion process with in situ amination and subsequent surface zwitterionicalization. PVC was directly reacted with triethylenetetramine (TETA) in casting solutions. The introduction of amino groups not only enhanced the hydrophilic property of PVC membranes but also provided the active chemical sites on the membrane surfaces. The aminated PVC membranes were then immersed into the sodium chloroacetate solution to carry out quaternary amination reaction. The zwitterionic groups were formed on the PVC membrane surfaces and pore walls. The surface chemical compositions of modified PVC membranes were confirmed by energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Water contact angle and zeta-potential measurement were employed to explore surface property. In the ultrafiltration experiment of bovine serum albumin (BSA) solution, the zwitterionic PVC membranes exhibited better permeability and fouling resistance ability than the initial PVC membrane. The corresponding resistances of membrane, cake formation, adsorption, and pore blocking were calculated to explore the membrane fouling mechanism.