Oil-polluted water mixtures are difficult to separate, and thus, they are considered as a global challenge. A superior superhydrophilic and low-adhesive underwater superoleophobic styrene-acrylate copolymer filtration membrane is constructed using a salt (NaOH)-induced phase-inversion approach. The as-fabricated filtration membrane provides a hierarchical-structured surface morphology and three-dimensional high density open-rough porous geometry with a special chemical composition including highly accessible hydrophilic −COO– agents, which all are of great importance for long-term usage of immiscible/emulsified (light) oil-polluted wastewater separation. The separation is performed with a high efficiency and a high flux under either a gravity-driven force or a small applied pressure of 0.1 bar. The filtration membrane indicates an excellent anti-fouling property and is easily recycled during multiple cycles. The outstanding performance of the filtration membrane in separating oil-polluted water mixtures and the cost-effective synthetic approach as well as commercially scaled-up initial materials all highlight its potential for practical applications.