A readout integrated circuit configured to read out sensing signals from an optical sensing panel is provided. The optical sensing panel includes a sensor array for fingerprint sensing. The readout integrated circuit includes a plurality of input terminals, a first discharging circuit and a control circuit. The plurality of input terminals are configured to be coupled to a plurality of output terminals of the optical sensing panel. The first discharging circuit is coupled to one of the plurality of input terminals. The first discharging circuit is configured to discharge one of the plurality of output terminals of the optical sensing panel by a first current during a readout period. The readout integrated circuit reads out a voltage of the output terminal as a sensing signal. The control circuit is coupled to the first discharging circuit. The control circuit is configured to output at least one control signal to control an operating period of the first discharging circuit.