The spatial wavelength of the hexagon pattern are studied for different discharge parameters in dielectric barrier discharge system near the atmospheric pressure. The generating process and the movement of the microdischarge channels are observed. It is found that the wavelength of the hexagon decreases as the applied voltage increases. It is also dependent upon the gas gap and the gas pressure. The new filaments appear near the discharge boundary when the applied voltage increases slowly. The filaments at the outmost vertexes of hexagon move along the radial axis. The filaments on the side of hexagon move along axis parallel to the C2 axis, which has the least distance to those filaments. The discharge spots change into discharge stripes and finally into the spiral or target pattern when the applied voltage is increased further. Based on the experimental results and the force analysis, the confined potential, which exists in two dimensional coulomb crystals, is proposed to exist in the discharge domain.