A circuit includes an impedance tuning circuit, a first antenna tuning switch and a resistor. An antenna end of the first antenna tuning switch is electrically connected with an external antenna signal source. A control end of the first antenna tuning switch is electrically connected with an external controller. A first RF output end of the first antenna tuning switch is electrically connected with one end of the resistor, and the other end of the resistor and a second RF output end of the first antenna tuning switch are electrically connected with one end of the impedance tuning circuit. The other end of the impedance tuning circuit is electrically connected with the antenna. The external controller controls the antenna end to be connected with the first RF output end or the second RF output end according to an SAR test result of the antenna.