This paper describes the AC discharge characteristics of air when a water droplet is on solid dielectric layers floating between the electrodes. Identical planar electrodes are used to experimentally examine the breakdown voltage during the tests. Experiments with a water droplet and vapor on the insulator surface are reported and breakdown voltage characteristics are presented. In the experiments, a single water droplet positioned in the center of horizontal dielectric layers made up of polyvinyl chloride. This insulating barrier has the same diameter with the electrodes. The dielectric behavior of insulating layer is investigated in the presence of water droplet and vaporous surface in various air gaps up to 50 mm and numerically analyzed by computer program using finite element method.