A tunable antenna is disclosed. The tunable antenna includes a ground element for providing grounding, a signal feed-in terminal, a radiation unit electrically connected to the signal feed-in terminal and including a long side extended from the signal feed-in terminal along a first direction, a short side extended from the signal feed-in terminal along a second direction, and a branch electrically connected between the signal feed-in terminal and the ground element, a coupling unit for coupling to the long side, and a switch unit for connecting or disconnecting the coupling unit to/from the ground element to change a coupling relationship between the coupling unit and the long side, such that the tunable antenna respectively operates in a first frequency band and a second frequency band.