An amplification circuit includes an input terminal, an output terminal, a capacitor, a bias unit, an amplification unit, and an impedance unit. The input terminal receives a radio frequency signal. The capacitor is coupled to the input terminal and the bias unit. The bias unit includes a transistor for controlling the bias current. The transistor has a first terminal for receiving a system voltage, and a control terminal coupled to the reference voltage terminal. The amplification unit has an input terminal coupled to the capacitor and the bias unit, and an output terminal coupled to the output terminal of the amplification circuit. The impedance unit has a first terminal coupled to the bias unit, and a second terminal coupled to the input terminal of the amplification circuit and the capacitor. The impedance unit adjusts the amplifying linearity of the amplification circuit according to a selection signal.