In recent decades, atmospheric-pressure plasma technology has been rapidly developed in the field of water treatment, and has a good application prospect, but it still remains a challenge to reduce operating energy consumption and improve processing efficiency for industrial applications. In this paper, a simple and industrially scalable prototype of plasma reactor based on dielectric barrier discharge (DBD) at atmospheric-pressure air condition is employed to the methylene blue(MB) simulated dye wastewater with complex structure and stable performance. The effects of discharge voltage, air volume, initial concentration, initial pH and initial conductivity on the treatment of methylene blue wastewater are studied. The contribution of .OH in the treatment of methylene blue wastewater by dielectric barrier discharge reactor is quantitatively analyzed. The study further uses the Box-Behnken response surface method to find the optimal operating parameters of the system: initial pH=4, discharge voltage 13kV, initial concentration 100mg/L. The results show that the device can effectively treat methylene blue wastewater. After 15 minutes of discharge under optimal conditions, the MB degradation rate was 95.39%, the energy efficiency was 14.87g/(kWh), the reaction rate constant was 0.2026 min-1, and reduction rate of the chemical oxygen demand (COD) value is 62.63%, the chromaticity change is also obvious, indicating that the device can be industrially applied to the treatment of organic dye wastewater.