A readout circuit for uncooled infrared focal plane arrays is successfully designed. The principle of the signal processing is studied and proper circuit is successfully designed and made to realize the signal processing. The feature of the signal processing circuit for the uncooled infrared focal plane array depends on the readout circuit Readout circuit discussed here is a RC oscillatory circuit. The resistor of the oscillatory circuit is VOx thin film, which is very sensitive to temperature. The relationship of the temperature and the period of the oscillatory circuit is discussed. The signal processing circuit employs the relationship to extract the temperature from the period of the output signal. The imaging processing part uses the extracted temperature information to get the infrared image.