The optical and electrical characteristics from filamentary discharge to pseudo-glow discharge are investigated by a specially designed optical detection systems. The discharges are initiated in mixture of air and argon at atmospheric pressure in a dielectric barrier discharge setup composed of two parallel planar electrodes separated by two layers of dielectric. The optical and electrical characteristics are displayed by the waveforms of the applied voltage, the discharge current and the emission spectral intensity. The waveforms of the applied voltage and the discharge current of two discharge modes have been recorded by oscilloscope. The emission spectra from the discharges are obtained through a spectrometer. When the other conditions are fixed the spectral intensity increases with the increase of voltage and driven frequency. The ratio of spectral intensity to the voltage in the filament discharge is smaller than that in the pseudo-glow discharge.