The present disclosure provides an antenna structure, including a feed terminal, an intermediate grounding terminal, a tail grounding terminal, a conductive head section and a conductive intermediate section. The feed terminal is for connecting a feed signal. The intermediate grounding terminal is responsible for conducting to a ground plane via an intermediate impedance during a second operation mode, and ceasing conducting via the intermediate impedance during a first operation mode. The tail grounding terminal is for connecting the ground plane. The head section extends from the feed terminal to the intermediate grounding terminal along a loop. The intermediate section extends from the intermediate grounding terminal to the tail grounding terminal along the loop.