Abstract: Activated carbons in powder and monolithic form easily form sediments in water, leading to the failure to adsorb an oil film on the water surface. To solve these problems, coconut shell activated carbons were modified to increase their oil-absorption ability and a 3D sponge-like activated carbon/organic composite was then prepared through polymerization of polyvinyl alcohol with formalin in the presence of a foaming agent and the modified activated carbon. The effects of the amounts of water, activated carbon, dilute sulfuric acid (9%) and formaldehyde solution (40%), and reaction temperature on the oil adsorption performance of the composites were investigated. The composites had a hierarchical porous structure and floated on the water surface due to their low density (about 0.197 7 g/cm³). A composite prepared under optimal conditions can adsorb approximately 1.5 times as much oil as the original activated carbon. Its robust and flexible properties make it suitable for recycling during use.