The electrical characteristics and vibrational temperature were investigated as functions of gas gap width, driving frequency and gas flow rate in flowing argon by using a dielectric barrier discharge device with transparent water electrodes. Electrical measurement results show that the discharge with a smaller gas gap width has a higher value of peak current and consumes more power than that with a larger gap width. Both the peak value of discharge current and consumed power increase monotonically with increasing the driving frequency, and decrease with increasing the gas flow rate. Through analyzing the vibrational systems of nitrogen molecule by optical emission spectroscopy, it was found that the vibrational temperature has a similar trend with the peak value of discharge current and consumed power by changing the driving frequency, gas gap width and gas flow rate. These results are important to the industrial applications of atmospheric pressure barrier discharge in flowing gas.