A meter-scale wide indirect dielectric barrier discharge (DBD) for treating large-scale and irregular-shaped materials is reported in this study. The structure of the modular-graded gas path is designed, and the influence of gas hole density on the flow field is simulated. It is confirmed that 8 subdividing (40 holes uniformly distributed) structure can effectively improve the uniformity of the gas flow rate distribution in the discharge area and on the treated material surface compared with 0 subdividing structure. Based on this structure, Ar is employed as the discharge gas and hexamethyldisilane as the precursor to generate meter-scale wide plasma under the excitation of a nanosecond pulsed power supply. Particle activity, discharge uniformity and stability under different operating parameters are evaluated by measuring voltage-current waveforms, emission spectra, luminescence images and temperatures at different electrode positions. The treatment effect and uniformity are verified by measuring the water contact angle (WCA) of epoxy (EP) material. The results show that a uniform and stable plasma with a width of 1120 mm is generated under suitable operating parameters. By increasing the voltage amplitude, both the discharge intensity and particle activity are improved, while the discharge uniformity and stability are significantly reduced. By increasing the discharge gas flow rate, the particle activity, discharge uniformity, and stability can be improved simultaneously but slightly. The WCA on the EP surface is uniformly increased from 67° to 144° with a variation of less than 6% after 10-min treatment at a voltage amplitude of 12 kV and a discharge gas flow rate of 10 L/min. The meter-scale wide indirect DBD electrode in this work can provide reference and basis for the industrial application of large-scale plasma material modification technology.