By using infrared detector and readout circuit, an uncooled infrared detecting system was developed. The detector using diode as the temperature sensor is compatible with integrated circuit process. A new device structure was used to improve the fill-factor from 20% to 80%. The area of micromachined structure is 35μm×35μm. The offset voltage of the readout circuit is 3μV. The output noise of the detector is 2μV. The responsivity of the detector is 7894.7V/W, specific detectivity of the detector is 1.56×109cmHz1/2/W, noise equivalent temperature difference of the detector is 330mK, and response time of the detector is 27 ms.