The wetting property of nanomaterials is of great importance to both fundamental understanding and potential applications. However, the study on the intrinsic wetting property of nanomaterials is interfered by organic capping agents, which are often used to lower the surface energy of nanomaterials and avoid their irreversible agglomeration. In this work, the wetting property of the nanostructured polyaniline that requires no organic capping agents is investigated. Compared to hydrophilic granular particulates, polyaniline nanofibers are amphiphilic and have an excellent capability of creating Pickering emulsions at a wide range of pH. It is suggested that polyaniline nanofibers can be easily wetted by water and oil. Furthermore, the amphiphilic polyaniline nanofibers as building blocks can be used to construct filtration membranes with a small pore size. The wetting layer of the continuous phase of emulsions in the porous nanochannels efficiently prevents the permeation of the dispersed phase, realizing high-efficiency on-demand emulsion separation.