The insulating property of water medium affects the operation state of pulse power device, and air bubbles in water are the main factor causing breakdown of water medium. To remove air bubbles and dissolved gases in the water medium, we analyzed the causes of air bubbles in the water medium. For the removal of body-phase air bubbles and surface adsorption air bubbles in the water medium, we compared the methods of removing air bubbles using vortex separators and reverse osmosis membranes, and we have carried out experimental research to study the performance of these two methods. The results show that the vortex separator’s low cyclonic strength leads to low separation (which can remove the gas bubbles and dissolved gases in the water) efficiency, and the reverse osmosis membrane degassing makes the surface adsorbed bubbles re-dissolve by reducing the solubility of the gas in the water, and the separation efficiency is high. This study is of great significance for the stable operation of the pulsed power device.