The absorption capacity of oily sludge pyrolysis residue was utilized to prepare oxygen-releasing composites for groundwater remediation. The physical properties of the oily sludge pyrolysis residue were specific surface area of 13.936 m(2)/g and main pore size on the order of nanometers. The pyrolysis residue was nontoxic and would not cause secondary contamination of groundwater. The rate of mass loss of calcium peroxide and the oxygen release rate in water were analyzed. An oxygen-releasing composite containing 35% calcium peroxide, 15% oily sludge pyrolysis residue, 30% fluviatile sand, 10% calcium-based bentonite soil, and 10% deionized water was proposed. Addition of oily sludge to the composite plugged some of the oxygen-releasing surface and slowed the rate of oxygen release. Continuous precipitation of CaCO3 on the surface and in the pores of the composite also reduced the initial oxygen release rate and slowed the overall oxygen release rate.