Bench and pilot scale experiments were conducted to investigate and compare the preoxidation effects of potassium permanganate (KMnO4) and ozone (O3) for odor removal in drinking water. The effects of dosage, contact time, pH, as well as couple treatment with a granular activated carbon (GAC) filter were examined using bench experiments, while the effects of KMnO4 dosing points and a preozonation coupled process were investigated in pilot scale tests. Results revealed that both preoxidants at appropriate dosage worked well for odor removal because of the strong oxidizing ability and the intermediates generated in the process. The preozonation rate of O3 was much faster than that of KMnO4. Preoxidation by KMnO4 was largely affected by pH because of the amount of hydrated manganese dioxide generated, which contributed to the adsorption of odorants. Pilot scale tests were highly synchronous with results of bench scale tests.