A novel deep eutectic solvent (DES) is proposed as a multifunctional porogen to simultaneously improve the permeability and selectivity of the polysulfate (PSE) ultrafiltration (UF) membrane. The effects of DES on the formation process of PSE membrane were explored by the viscosity, cloud point, and phase inversion properties. The molecular weight cutoff (MWCO) of the prepared membranes decreased as the DES content increased to 3.0 wt%, reaching as small as 18.5 kDa, with an improved porosity of 81.9%. In addition, the water flux improved to 212.3 L/m2*h, which was 2.3-fold larger than that of the pristine PSE membrane, and the rejection efficiency for natural organic matter (NOM) was simultaneously enhanced. Considering the easy and cheap preparation of the DESs, the proposed method offers a new possibility for high-performance UF membranes preparation.