The invention discloses an oil-water separation device and a preparation method thereof, and belongs to the technical field of chemical process devices. The preparation method comprises the following steps of: alternately putting a foam metal mesh substrate into ethanol and acetone, ultrasonically cleaning, and drying; preparing the required hydrofluoric acid / silver nitrate corrosive liquid; closely combining the foam metal mesh and a silicon chip, immersing in the heated hydrofluoric acid / silver nitrate corrosive liquid, corroding for 5 to 20 minutes, taking out, washing with distilled water, and drying; and soaking the dried device in ethanol solution of a low-surface-energy substance, taking out, washing with distilled water and drying. The device with multiple functions of adsorbing overflowed oil, an oil skimmer and separating oil and water consists of the metal mesh substrate and nano metal silver particles deposited on the surface of the metal mesh substrate, and has the surface modified by the low-surface-energy substance. The device has superhydrophobic / super-oleophilic effect, can be self-cleaned, can bear high temperature of at least 120DEG C, and can collect leaked oil at high temperature. The preparation method is simple, the flow time is short, and the efficiency is high.