Abstract A kind of novel water treatment device by non-thermal plasma was proposed. Water was atomized by nozzle discharge electrode supplied with high voltage. Chance of the reaction between the non-thermal plasma and the contamination in the water was improved. Non-thermal plasma, especially hydroxyl radicals was measured near the nozzle-discharge electrode with water injected into the treatment chamber through the nozzle by optical emission spectroscopy. Hydroxyl radicals produced in this device was proved. The effect of negative direct current corona discharge, positive direct current corona discharge and negative pulsed discharge on the hydroxyl radicals’ production was investigated. In addition, the electric characteristics of the device were given.