Abstract: To address the challenge of treating strongly alkaline, highly stable, emulsified oily 1wastewater generated during electroplating pretreatment processes, a structure-function-integrated TA-PEI/PES modified ultrafiltration membrane was developed using the intermolecular synergistic effects between tannic acid (TA) and polyethylenimine (PEI), through physical blending and solvent-induced phase separation technology. The effects of TA-PEI loading on the membrane’s microstructure, hydrophilicity, mechanical properties, ultrafiltration performance, oil-water separation performance, and alkali resistance were systematically investigated. The study found that TA and PEI formed a stable hydrophilic network within the membrane through covalent cross-linking and hydrogen bonding, significantly improving interfacial wettability. When the TA-PEI loading was 1.5 wt%, the pure water flux increased to 273.1 L/(m²·h) - approximately six times that of the polyethersulfone (PES) membrane - while maintaining a protein retention rate of over 96.39%. Additionally, the modified membrane exhibited excellent anti-fouling properties, with a flux recovery rate of 72.06% and an enhanced separation efficiency of 91.35% for oil-in-water emulsions. Furthermore, after soaking in a strongly alkaline solution (pH 12) for 72 h, the modified membrane still maintained stable permeate flux and separation efficiency, demonstrating excellent chemical resistance. This modification strategy not only achieved a simultaneous improvement in membrane flux and anti-fouling performance but also significantly enhanced the operational stability of the membrane material under strongly alkaline conditions, providing an effective approach for the resource recovery and closed-loop reuse of oily wastewater from electroplating pretreatment.