Disclosed is a structure for detecting the vibration displacement of a speaker, including: a vibration system having a movable pole plate; a magnetic circuit system; and a fixed pole plate provided under the vibration system and opposite to the movable pole plate, the movable pole plate and the fixed pole plate constituting a capacitor. Also disclosed is an acoustoelectric inter-conversion dual-effect device, further including an impedance transformer connected to the capacitor and including a field effect transistor and a diode. In the present invention, a movable pole plate of a capacitor is provided on a vibration system and a fixed pole plate is provided under the vibration system and fixed in position. When the vibration system vibrates, the change in capacitance is detected to calculate the actual displacement of the vibration system, which can reduce the power of the speaker device when the actual displacement of the vibration system exceeds a safety threshold. For an electronic device adopting such a speaker structure, the displacement of the vibration system of a speaker product can be detected in real time at the system end of the electronic device.