[en] The Atmospheric Pressure Glow Discharge was observed in a surface discharge generator. The frequency of ac power supply is more than 10 kHz and the sinusoidal peak-to-peak applied voltage is 12 kV. The electric field intensities in two kinds of surface discharge generators are calculated by the Boundary Element Method. Then a two-dimensional fluid model was used to simulate the ion trapping and electron trapping in a surface discharge just before the discharge. The simulation results are in good agreement with the observation