Non-thermal plasma treatment by an electrical discharge generated above water was applied to study the destruction of anthraquinonic dye Acid Blue 25 in aqueous solutions. The direct current glow discharge above water sustaining in ambient air was used as a source of non-equilibrium plasma. The effect of operational parameters such as initial dye concentration, discharge current, pH and addition of salts on the substrate degradation was investigated. The highest G 50 value was obtained for 45 mA current at low solution conductivity and G50 value was about 2.4 g/kWh. The degradation efficiency of AB25 in distilled water was compared with those in complex matrices such as natural and sea waters. It is shown that the degradation in natural matrices is less effective due to presence of OH radicals scavengers like HCO3-. The intermediates of AB25 dye destruction were studied by means of HPLC with multi-wavelength detector and combination of HPLC with time-of-flight mass-spectroscopy.