Abstract: Dielectric barrier discharge is a method for generating stable plasma with high power at atmospheric pressure. It finds wide applications in material surface modification, plasma medicine and environmental protection. Experimental, theoretical analysis and simulation methods are carried out to better understand the influence of gas gap distance on dielectric barrier discharge in this paper. The transition from filament to uniform mode in dielectric barrier discharge is simulated. It is shown that for a certain gas, an increase in gas gap distance leads to a decrease of the electric field intensity in the gas gap distance; a higher voltage is required to maintain the discharge. The gas gap has a significant impact on the discharge mode transition of dielectric barrier discharge. When the electric field intensity generated by the space charges and accumulated charges on the dielectric surface predominated, the discharge transform from the filament mode to the uniform one. The results have guiding significance for the design and optimization of dielectric barrier discharge devices.