A capacitive detection device, a method and a pressure detection system are provided. The capacitive detection device includes a differential amplifier, a first capacitor, a second capacitor, a charging module, a control module and a calculation module. The charging module is controlled by the control module to charge two capacitors to be detected, then an amount of charge of the capacitors to be detected is transferred to the first capacitor and the second capacitor, and a signal is amplified through the differential amplifier and the amplified signal is output to the calculation module, so that a capacitance difference of different capacitors may be obtained through a voltage at an output terminal of the differential amplifier, a supply voltage of the charging module, a capacitance of the first capacitor and a capacitance of the second capacitor.