Monolithic silica with macroporous skeleton and well-defined mesopores was prepared via sol–gel method by using triblock polymer P123 as the structure directing agent and tetramethoxysilane (TMOS) as the silicon source. The large macroporous channels (3 μm in diameter), formed by phase separation and sol–gel transition, ensure the substances diffuse in the bulk easily. Appropriate specific area (nearly 400 cm² g⁻¹) and mesopores (17.67 nm in diameter and 1.99 cm³ g⁻¹ in volume) supply enough space for storing the molecules absorbed. After grafting organic groups on their surface, hydrophobic monolithic hierarchically porous silica (MHS) could be prepared with high capability to adsorb oils and organic contaminants on the surface of water without coadsorption. In order to explore the factors impacting the ability of adsorption, a series of properties are characterized including the BET surface, porous size and water contact angle by changing the type and dosage of modifying agents. The maximum absorptive ability can reach 8 times the monolith's weight, and materials could be recycled more than 20 times by an easy treatment. Good selectivity, better thermal stability, easy removing and excellent recyclability for oil removal give the material potential applications.