Abstract: Even though the oscillating jet actuator has been widely utilized in flow control, its control mechanism still requires substantial fundamental research. This paper conducted numerical simulations on controlling separated flow fields around a deflection flap using several oscillating jet actuators to identify the key factors affecting the control effect. By studying the control effect of different expansion sections and comparing the control characteristics of pulse and sweep oscillating jets, the causes and effects of jet stagnation and the influence of the jet's sweeping extent on the control effect are summarized. The results show that the uniformity of the momentum transferred by the jet into the flow field and the sweeping extent are the key factors affecting the control effect. A more uniform momentum transferred by the jet into the flow field and a larger sweeping extent yield a better control effect. If the actuator throat is too small, the jet will stagnate on both sides of the outlet due to a restrained deflection. This results in the uneven momentum transfer from the jet into the flow field and a better control effect on both sides of the deflected flap than that in the middle. Increasing the expansion section will increase the sweeping extent of the jet and improve the control effect. The wedge in the pulse exciter prevents the jet from sweeping to its rear, yielding a small sweeping extent of the jet and a worse control effect in the middle of the deflected flap.