Appling a high voltage to the dielectric barrier discharge device in a coaxial geometry in flowing argon, a uniform plasma plume is generated at one atmospheric pressure. The waveforms of discharge current and the applied voltage are investigated and results indicate that both the intensity and duration width of the discharge current pulse increase with increasing the applied voltage. The gas temperature of the plasma plume is investigated by using an infrared thermometer. The gas temperature of the plasma plume are functions of gas flow rate, peak value and the frequency of the applied voltage. Results show that the gas temperature increases with increasing the applied voltage or its frequency, while it decreases with increasing the gas flow rate. A qualitative explanation is given for the variance of gas temperature as functions of the experimental parameters by analyzing the waveforms of the discharge current and the applied voltage.