A capacitance sensing circuit for sensing a capacitance of a detecting circuit, wherein, the detecting circuit receives an input signal and generates an output signal, the capacitance sensing circuit comprises: a capacitance judging circuit coupled to the detecting circuit and configured to judge a capacitance of the detection capacitor according to the output signal; and an input signal generator coupled to the detecting circuit and configured to generate the input signal according to noise, the input signal generator comprises: a phase detection unit configured to receive the noise and detect a first phase of the noise; a phase calculation unit (142, 242, 342, 442, 542, 642, 742) coupled to the phase detection unit and configured to receive the noise and the first phase, and calculate an optimum phase of the input signal according to the noise and the first phase to minimize the energy associated with the noise in the output signal; and a first waveform generator coupled to the phase calculation unit, and configured to generate the input signal according to said optimum phase; characterized in that, the phase calculation unit comprises a plurality of charge transfer circuits, the plurality of charge transfer circuits are controlled by a plurality of control signals, the plurality of control signals have a plurality of phases, the plurality of charge transfer circuits generate a plurality of charge output signals according to the noise; and the phase calculation unit calculates said optimum phase according to the plurality of charge output signals. a capacitance judging circuit coupled to the detecting circuit and configured to judge a capacitance of the detection capacitor according to the output signal; and an input signal generator coupled to the detecting circuit and configured to generate the input signal according to noise, the input signal generator comprises: a phase detection unit configured to receive the noise and detect a first phase of the noise; a phase calculation unit (142, 242, 342, 442, 542, 642, 742) coupled to the phase detection unit and configured to receive the noise and the first phase, and calculate an optimum phase of the input signal according to the noise and the first phase to minimize the energy associated with the noise in the output signal; and a phase detection unit configured to receive the noise and detect a first phase of the noise; a phase calculation unit (142, 242, 342, 442, 542, 642, 742) coupled to the phase detection unit and configured to receive the noise and the first phase, and calculate an optimum phase of the input signal according to the noise and the first phase to minimize the energy associated with the noise in the output signal; and a first waveform generator coupled to the phase calculation unit, and configured to generate the input signal according to said optimum phase; characterized in that, the phase calculation unit comprises a plurality of charge transfer circuits, the plurality of charge transfer circuits are controlled by a plurality of control signals, the plurality of control signals have a plurality of phases, the plurality of charge transfer circuits generate a plurality of charge output signals according to the noise; and the phase calculation unit calculates said optimum phase according to the plurality of charge output signals.