Abstract: To investigate the flow control characteristics of a dual synthetic jet in thrust vectoring, the peak velocity and excitation frequency of the dual synthetic jet were adjusted to reveal its control mechanisms over the nozzle mainstream deflection. The dynamic mode decomposition method was applied to extract and analyze the dominant flow field modes. Concurrently, an external flow of 34 m/s was applied to examine the mainstream deflection in the nozzle coupled with a flying wing structure. Results indicate that increasing the peak velocity of the dual synthetic jet expands the influence range of the low-pressure region in the flow field, leading to an increase in the mainstream deflection angle to 22°. Elevating the excitation frequency of the dual synthetic jet promotes the growth of the mainstream deflection angle, which tends to stabilize when the frequency exceeds 100 Hz. Regarding the flow control mechanism: during the suction cycle, the ventral orifice of the dual synthetic jet ingests the mainstream, forming a localized low-pressure region that induces mainstream deflection; during the blowing cycle, the mainstream recenters, causing the formation of wall-attached separation vortices on the downstream wall. The dorsal orifice exhibits a critical vortex entrainment and ejection effect that accelerates the passive secondary flow. Further dynamic mode decomposition analysis revealed dominant vorticity and velocity fluctuations occurring both at the location of the dual synthetic jet installation and on the downstream wall. This demonstrates that the dual synthetic jet, despite its minimal energy contribution, governs the modal characteristics of the flow field, while the downstream wall enhances the mainstream deflection. Simultaneously, simulation studies on the flying-wing-coupled nozzle revealed that the current configuration induces flow recirculation on the upper wall, which suppresses the nozzle's mainstream deflection, resulting in a maximum deflection angle of only 10°.