A dual synthetic jet (DSJ) actuator with an adjustable slider is designed and manufactured. A new evaluation method for the vectoring characteristic of the DSJ is proposed based on its potential-core momentum. The solved vectoring angle of the DSJ represents the direction of its potential-core momentum. This evaluation method can effectively reduce the errors resulted from the unsteadiness and the bad repeatability of the DSJ flow-field, comparing to the prior evaluation methods that depend on scalar coordinates of prescribed points The vectoring angle can be adjusted from -38.8 to 30.99 deg by controlling the movement of the adjustable slider, which indicates that the control performance of the DSJ is effectively extended. As demonstrated in the flow-field visualization, good agreement is found between the schlieren and PIV experimental results on the vectoring deflection of the DSJ, and the DSJ deflects toward the side of the slot with a greater width.