Ultrasound-assisted　regeneration　of　powdered　activated　carbon　(PAC)　saturated　with　4-chlorophenol　(4-CP)　was　investigated　in　this　work.　The　variables,　i.e.,　acoustic　frequency,　density　levels,　regenerating　solution　species,　spent　PAC　mass,　and　the　number　of　repeated　cycle,　were　optimized.　The　UV-Vis　spectra,　thermogravimetric　analysis　(TGA),　Fourier　transform　infrared　spectroscopy　(FT-IR),　scanning　electron　microscopy　(SEM),　Brunauer-Emmett-Teller　(BET),　and　pore　structure　analysis　were　used　to　characterize　the　regenerated　PAC　as　compared　to　the　virgin　and　spent　PAC.　The　adsorption　experiments　indicated　that　the　adsorption　kinetics　of　4-CP　fitted　well　with　the　pseudo-second-order　model,　and　the　main　chemisorption　process　was　nonlinear　and　heterogeneous.　The　desorption　results　showed　that　the　optimized　regenerated　conditions　were　identified　as　40　kHz　of　frequency,　0.18　W/mL　of　sonication　intensity,　0.1　M　NaOH　and　50%　(v/v)　ethyl　alcohol　mixture　of　regeneration　solution,　and　1　g/L　of　saturated　PAC　mass.　Under　this　condition,　the　regeneration　efficiency　reached　up　to　86.81%.　Hydroxylated　oxidation　products　especially　benzoquinone　and　hydroquinone　were　formed　during　ultrasound　regeneration.　Ultrasound　mainly　acted　on　surface　functionalities,　mesopores,　and　macropores　of　PAC　through　the　hydroxyl　radical　oxidization　resulted　from　the　cavitation　effect.