Abstract: The mechanism responsible for discharge channel contracting in RF single dielectric barrier discharge (RF-SDBD) at atmospheric pressure was investigated by using lab-built RF-SDBD device, which composed of a powered brass electrode covered by fused-silica as a dielectric layer and a grounded brass electrode cooled by recycled water.The discharge channel contracting in atmospheric nitrogen/argon mixtures was explored with nano-second intensified charge coupled device (ns-ICCD) camera.The discharge channel shape remained unchanged, but the intensity of light emission was changed periodically with the cycle of RF power.It was noticed from spatio-temporal image and temporally resolved image that the intensity peak of light emission near the upper electrode and the bottom electrode alternately appeared during one cycle of RF, but the time interval between the two peaks was not equal to one half cycle of RF.This phenomena was quite different from discharge channel formation in RF discharge with bared electrodes, or RF double dielectric barrier discharge.We suggested that the significant differences of deposited charges and secondary electron emission between the surfaces of the upper brass electrode and the dielectric covered the bottom electrode under non-symmetric electrode structure may explain the discharge channel contracting in RF-SDBD.