Herein, a durable superhydrophobic/superoleophilic membrane with micro-/nano-hierarchical structure was achieved through molecular and structural design of fluorinated polyacrylonitrile-based membrane. In which, the introduction of perfluorooctanol acrylate into copolymer chain and usage of electrospinning/electrospraying technology followed by heat post-treatment provided low surface energy and durable hierarchical structure, respectively. The resultant membrane demonstrated superhydrophobicity and superoleophilicity with water contact angle of 160° and oil contact angle of 0° in air, which endowed the membrane with excellent separation ability for oil/water mixture with separation efficiency above 99% and ultrahigh flux beyond 8000 L/m²/h. Furthermore, the obtained membrane maintained its superhydrophobicity after exposure to broad pH, organic solvents, high temperature and ultrasonic treatment, ascribed to the chemical reaction of cyano groups on the surface of fibers and particles during the heat post-treatment. This work provides a promising strategy to fabricate superwetting membrane to remove trace amount of water in oil.