Abstract: The water falling film dielectric barrier discharge(DBD) reactor can efficiently generate gaseous reactive species, and its large gas-liquid reaction interface is conducive to the mass transfer of gaseous reactive species into solution for an efficient degradation of aqueous pollutants. We studied the effect of pulse polarity on the discharge characteristics and the degradation of sulfamethoxazole(SMX) in a water falling film pulsed DBD reactor. It is found that the electric discharge was stronger and the SMX degradation efficiency was higher when water falling film reactor was powered by a bipolar pulse power supply, compared to unipolar pulse generators. Moreover, the effects of bipolar pulse voltage and frequency, initial concentration of SMX and pH value on the degradation of SMX were investigated, and the degradation mechanism of SMX was also analyzed. The results show that the discharge power and the degradation efficiency of SMX will increase with the discharge voltage and pulse frequency. When the discharge voltage is low, an increase in applied voltage will result in higher SMX degradation efficiency and energy efficiency, but an elevating pulse frequency usually decreases the energy efficiency. Solution recycling flow rate and conductivity have a negligible effect on the degradation of SMX. At a discharge power of 5 W, the degradation efficiency of SMX reaches 80.2% after 200 mL 20 mg/L SMX solution is treated for 30 minutes, at this time the energy efficiency is 1.28 g/(kW·h). Due to the ozonation and protonation of SMX molecules, the degradation efficiency of SMX at alkaline pH values is much higher compared to acidic conditions.