Developing a feasible and efficient separation membrane for the purification of highly emulsified oily wastewater is of significance but challenging due to the critical limitations of low flux and serious membrane fouling. Herein, a biomimetic and superwettable nanofibrous skin on an electrospun fibrous membrane via a facile strategy of synchronous electrospraying and electrospinning is created. The obtained nanofibrous skin possesses a lotus-leaf-like micro/nanostructured surface with intriguing superhydrophilicity and underwater superoleophobicity, which are due to the synergistic effect of the hierarchical roughness and hydrophilic polymeric matrix. The ultrathin, high porosity, sub-micrometer porous skin layer results in the composite nanofibrous membranes exhibiting superior performances for separating both highly emulsified surfactant-free and surfactant-stabilized oil-in-water emulsions. An ultrahigh permeation flux of up to 5152 L m(-2) h(-1) with a separation efficiency of >99.93% is obtained solely under the driving of gravity (approximate to 1 kPa), which was one order of magnitude higher than that of conventional filtration membranes with similar separation properties, showing significant applicability for energy-saving filtration. Moreover, with the advantage of an excellent antioil fouling property, the membrane exhibits robust reusability for long-term separation, which is promising for large-scale oily wastewater remediation.