Abstract: Even though the dual synthetic jet, a novel active flow control method with simple configuration and rapid response, does not suffer from the diaphragm failure problem common for regular synthetic jets, its performance is prone to be affected by the geometry of the jet orifice. This paper systematically studies the performance of 25 groups of dual synthetic jet actuators with different rectangular jet orifices using Particle Image Velocimetry (PIV) and numerical simulations. Specifically, the relationship between flow structures and the frequency characteristics at the jet orifice is obtained by PIV. The effects of the jet orifice's geometry on the Helmholtz resonance frequency of the actuator cavity are analyzed, yielding the optimal R_AR-R_DLR relationship. Numerical simulations are used to explore the influence of the jet orifice’s geometry on the jet velocity distribution and shaft-switching phenomenon. The results show that rectangular jet orifices with small aspect ratios produce more concentrated jet velocity with higher peak magnitude. In contrast, the velocity magnitude at rectangular jet orifices with large aspect ratios is lower; a single jet can be deflected easily by the pressure difference, but the energy exchange with the ambient fluid is more remarkable.