A fingerprint identification sensor, applicable to a terminal device, comprising: a sensor unit, comprising a capacitor array formed by a plurality of capacitor induction units, and having an output, a power supply and a sensor ground, the output outputting a driving signal; and a modulation circuit, connected to a device ground of the terminal device, and the output, the power supply and the sensor ground of the sensor unit, and configured to, upon modulating the driving signal to a modulated signal, output the modulated signal to the sensor ground, wherein a voltage of the power supply varies with the modulated signal; characterized in that the modulation circuit comprises: a conversion circuit, connected to the device ground of the terminal device, and the output and the sensor ground of the sensor unit, and configured to, upon modulating the driving signal to the modulated signal, output the modulated signal to the sensor ground; an energy storage capacitor, connected between the power supply and the sensor ground, and configured to stabilize an operating voltage of the sensor unit; a high-speed transistor switch, connected to the power supply, and configured to perform synchronous switch-on and switch-off according to status of the conversion circuit, such that a voltage of the power supply varies with the modulated signal; and a power source, connected to the conversion circuit and the power supply of the sensor unit via the high-speed transistor switch to supply power for the conversion circuit and the sensor unit; wherein a supply voltage supplied by the power source is provided to the power supply of the sensor unit via the high-speed transistor switch, so that the operating voltage between the power supply and sensor ground of the sensor unit is maintained at the supply voltage supplied by the power source; wherein the sensor ground of the sensor unit and the device ground of the terminal device are connected in a low level of the driving signal. a sensor unit, comprising a capacitor array formed by a plurality of capacitor induction units, and having an output, a power supply and a sensor ground, the output outputting a driving signal; and a modulation circuit, connected to a device ground of the terminal device, and the output, the power supply and the sensor ground of the sensor unit, and configured to, upon modulating the driving signal to a modulated signal, output the modulated signal to the sensor ground, wherein a voltage of the power supply varies with the modulated signal; characterized in that the modulation circuit comprises: a conversion circuit, connected to the device ground of the terminal device, and the output and the sensor ground of the sensor unit, and configured to, upon modulating the driving signal to the modulated signal, output the modulated signal to the sensor ground; an energy storage capacitor, connected between the power supply and the sensor ground, and configured to stabilize an operating voltage of the sensor unit; a high-speed transistor switch, connected to the power supply, and configured to perform synchronous switch-on and switch-off according to status of the conversion circuit, such that a voltage of the power supply varies with the modulated signal; and a power source, connected to the conversion circuit and the power supply of the sensor unit via the high-speed transistor switch to supply power for the conversion circuit and the sensor unit; wherein a supply voltage supplied by the power source is provided to the power supply of the sensor unit via the high-speed transistor switch, so that the operating voltage between the power supply and sensor ground of the sensor unit is maintained at the supply voltage supplied by the power source; wherein the sensor ground of the sensor unit and the device ground of the terminal device are connected in a low level of the driving signal. a conversion circuit, connected to the device ground of the terminal device, and the output and the sensor ground of the sensor unit, and configured to, upon modulating the driving signal to the modulated signal, output the modulated signal to the sensor ground; an energy storage capacitor, connected between the power supply and the sensor ground, and configured to stabilize an operating voltage of the sensor unit; a high-speed transistor switch, connected to the power supply, and configured to perform synchronous switch-on and switch-off according to status of the conversion circuit, such that a voltage of the power supply varies with the modulated signal; and a power source, connected to the conversion circuit and the power supply of the sensor unit via the high-speed transistor switch to supply power for the conversion circuit and the sensor unit; wherein a supply voltage supplied by the power source is provided to the power supply of the sensor unit via the high-speed transistor switch, so that the operating voltage between the power supply and sensor ground of the sensor unit is maintained at the supply voltage supplied by the power source; wherein the sensor ground of the sensor unit and the device ground of the terminal device are connected in a low level of the driving signal.