Effective separation of oil/water emulsion and removal of organic dyes are of critical importance for environmental protection. In this study, superhydrophobic polyacrylonitrile (PAN) nanofibrous membrane embedded Au nanoparticles (NPs) in cavity has been prepared through a facile electrospinning and subsequent surface-modification strategy. The as-prepared [email protected]@PAN-TD membrane exhibited a water contact angle (WCA: ∼155.5°), an oil contact angle in air (OCA: ∼0°) and a WCA under-oil (∼158°). The composite membrane has demonstrated its ability to achieve efficient water/oil separation and in situ catalytic degradation of organic dye (e.g. 4-nitrophenol). The superhydrophobic [email protected]@PAN-TD membrane with a hierarchical porous structure would open an avenue for the purification of polluted oily water system.