Material with special wettability for oil/water separation has drawn more and more attention, since the oil spill accidents and industrial processing are growing in frequency and in volume. A superhydrophilic and underwater superoleophobic mesh was prepared by introducing Co3O4 on a stainless steel mesh, through a simple hydrothermal process and subsequent calcination. The as-prepared Co3O4 mesh can not only separate various oil/water mixtures with high efficiency and high flux, but also work effectively in harsh environment such as highly acidic, alkaline, and salty solutions. Moreover, the Co3O4 mesh can still retain good separation performance after 40 abrasion cycles with sandpaper. The outstanding anticorrosion and antiabrasion behaviors make the Co3O4 mesh promising for oil/water separation even in harsh environment.