<p>Due to the strong adhesiveness of polydopamine, Ag⁺ can be fixed on the surface of the cotton fabric. Then, through the self-organization of octadecyltrichlorosilane (ODTS), a superhydrophobic and a superoleophilic cotton fabric can be obtained. A scanning electron microscope (SEM), a Fourier transform infrared spectrometer (FTIR), a thermogravimetric–differential thermal analyzer (TG), and a contact angle measuring device are used to evaluate the surface morphology and wettability of the cotton fabric. From the results of the contact angle and the surface wettability, it is found that the modified cotton fabric shows excellent hydrophobicity. The contact angle with water can reach 156.8°. Water droplets can stay spherical on its surface for a long time without spreading or wetting the fabric. Furthermore, it also exhibits good lipophilicity and can quickly absorb oil droplets that land on its surface. The fabricated fabric can effectively achieve oil–water separation through the action of gravity. The separation efficiency for various types of oil–water separation exceeds 98% and can reach a maximum of 99.89%. Additionally, the superhydrophobic cotton fabric also has the ability to separate water-in-oil emulsions with different volume ratios more effectively. The modified fabrics can inhibit the growth of <i>E. coli and S. aureus</i>, showing good antibacterial properties.</p>