Three tests were conducted using ultrasound alone, ultrasound as an enhancement for electrokinetic test and electrokinetic test alone to compare the removal performance of the three persistent organic pollutants, hexachlorobenzene, phenanthrene, and fluoranthene from low permeability kaolin. Results show that the removal efficiency in ultrasonically enhanced electrokinetic test was the highest among experiments, though the removal rates improved were small only. The assistance of ultrasound in electrokinetic remediation can help reduce these hydrophobic organic compounds by increasing their mobility, desorption for electroosmotic migration, and also by degrading them through free radical oxidation forming during cavitation process.