Functional membranes that are both robust and porous with selective wettability find widespread application in oil/water separation processes. This study used polyacrylonitrile (PAN), surfactant-modified cellulose nanocrystals (H-CNC) and polyvinylpyrrolidone (PVP) as the raw materials to prepare a nanofibrous membrane (HCNC/PPAN) with a strong loess-beam-like structure using the electrospinning and sacrificing template strategy. Surfactant adsorption enabled stable dispersion of H-CNC within the polymer matrix. The tensile strength and Young's modulus were 7.46 +/- 0.36 MPa and 150.66 +/- 33.12 MPa, respectively, which represent an increase by 3.15 times and 1.89 times when compared to the corresponding values of the PAN membrane. The H-CNC/PPAN membrane obtained a good pore size distribution after removing PVP by water etching, as a result of the formation of furrows and micro-meso-pores. Moreover, the etching process effectively improved the mechanical properties of the membranes. Based on the presence of hydroxyl and amide groups on the membrane surface, the membrane displayed pre-wetting induced underwater superoleophobicity and underoil superhydrophobicity. Driven by gravity, an ultra-high permeation flux of 7210.51 L & sdot;m � 2 & sdot;h- 1 and a separation efficiency of over 98.93% were achieved. Thanks to its excellent oil repellency and good resistance to acid, alkali and salt, the HCNC/PAN membrane is highly sustainable and has broad potential applications in the field of oil/water separation.