A control circuit of a power amplifier, comprising: a peak detector, configured to detect an amplitude of an input signal; and a bias circuit, configured to generate a bias voltage to the power amplifier, wherein the bias circuit is configured to generate the bias voltage to a varactor (222, 224) connected to an input terminal of the power amplifier, to control a capacitance of the varactor (222, 224) in order to compensate the nonlinearity of the input capacitance of the power amplifier, and characterized in that: when the amplitude of the input signal continuously increases, the bias circuit is configured to generate the bias voltage to increases the capacitance of the varactor (222, 224), and then to decrease the capacitance of the varactor (222, 224); wherein the control circuit further comprises: at least a first comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a first threshold to generate a first comparing result; a first current source, coupled to the first comparator, configured to generate a first current according to the first comparing result; at least a second comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a second threshold to generate a second comparing result; and a second current source, coupled to the second comparator, configured to generate a second current according to the second comparing result; wherein the bias circuit is coupled to the first current source and the second current source and is configured to generate the bias voltage according to the first current and the second current. a peak detector, configured to detect an amplitude of an input signal; and a bias circuit, configured to generate a bias voltage to the power amplifier, wherein the bias circuit is configured to generate the bias voltage to a varactor (222, 224) connected to an input terminal of the power amplifier, to control a capacitance of the varactor (222, 224) in order to compensate the nonlinearity of the input capacitance of the power amplifier, and characterized in that: when the amplitude of the input signal continuously increases, the bias circuit is configured to generate the bias voltage to increases the capacitance of the varactor (222, 224), and then to decrease the capacitance of the varactor (222, 224); wherein the control circuit further comprises: at least a first comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a first threshold to generate a first comparing result; a first current source, coupled to the first comparator, configured to generate a first current according to the first comparing result; at least a second comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a second threshold to generate a second comparing result; and a second current source, coupled to the second comparator, configured to generate a second current according to the second comparing result; wherein the bias circuit is coupled to the first current source and the second current source and is configured to generate the bias voltage according to the first current and the second current. when the amplitude of the input signal continuously increases, the bias circuit is configured to generate the bias voltage to increases the capacitance of the varactor (222, 224), and then to decrease the capacitance of the varactor (222, 224); wherein the control circuit further comprises: at least a first comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a first threshold to generate a first comparing result; a first current source, coupled to the first comparator, configured to generate a first current according to the first comparing result; at least a second comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a second threshold to generate a second comparing result; and a second current source, coupled to the second comparator, configured to generate a second current according to the second comparing result; at least a first comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a first threshold to generate a first comparing result; a first current source, coupled to the first comparator, configured to generate a first current according to the first comparing result; at least a second comparator, coupled to the peak detector, configured to compare the amplitude of the input signal with a second threshold to generate a second comparing result; and a second current source, coupled to the second comparator, configured to generate a second current according to the second comparing result; wherein the bias circuit is coupled to the first current source and the second current source and is configured to generate the bias voltage according to the first current and the second current.