In this work, a brand new one-step in situ thermal polymerization (ISTP) preparation of highly stable polymer-coated superhydrophobic materials has been reported. On the basis of the thermal initiation and nonvolatility of an ionic liquid (IL) precursor, robust polymeric layer could be in situ generated and coated to meshes under air atmosphere, while the anchored nanoparticles could provide hierarchical micro/nanostructure. An "oxidative crosslinking" effect was found, and the possible mechanism was proposed. As expected, the obtained mesh exhibited superhydrophobicity with water CA of 158 degrees and superoleophilicity with oil CA of 0 degrees. Besides, the mesh showed self-cleaning effect with a low sliding angle. As for application evaluation, the mesh could act as a filter for the highly efficient separation of a series of oil-water mixtures. More importantly, the mesh exhibited excellent stability and durability toward ultrasonic, abrasion treatment, long-term storage, and even under strongly acidic, alkaline, and saline environment conditions. In summary, this work provided a novel, facile, and scalable method in the fabrication of superhydrophobic surface.