Abstract: The inherent tendency of atmospheric air dielectric barrier discharges (DBDs) to transition into a filamentary mode severely restricts their application in large-area, uniform plasma processing. To overcome this fundamental limitation, this study demonstrates a novel synergistic dual-power-driven strategy for achieving a stable, homogeneous nanosecond-pulsed DBD. A dedicated triple-electrode dielectric barrier discharge (DBD) reactor was designed, where an AC auxiliary discharge preconditions the main gap prior to the application of the primary nanosecond pulse. Experimental results demonstrate that this approach remarkably reduces the discharge sustaining voltage from 13.5 kV to 12.5 kV and enhances the single-pulse energy deposition, evidenced by a ~ 3.6-fold increase in charge transfer. Most significantly, intensified charge-coupled device (ICCD) imaging confirms a complete transition from a filamentary to a homogeneous diffuse discharge mode. Although the breakdown voltage remains unchanged, the performance leap is driven primarily by the auxiliary discharge’s dual role in pre-ionization and electric field homogenization. This work provides a practical and effective solution for generating uniform air plasma, with immediate implications for improving the efficiency and consistency of applications in environmental remediation and material surface modification.