Abstract: To design low-temperature CMOS circuit for low impedance infrared photoconductive detector and realizing high performance IR imaging, the use of differential amplifier with symmetrical positive and negative power is necessary. Thus, a kind of two grade CMOS circuit was designed. The first grade was adopted bridge circuit input, this structure was fit for low impedance detector. The positive magnifying method was introduced in second grade. The feedback resistance was designed 1 M, the circuit was supplied by 1.5 V and this circuit was attached to detector without capacitance. The testing results show that the amplifier can work well when it connects with low-impedance infrared photoconductive detector at the low temperature. The circuit total gain exceeds 10 000 times, the 3 dB bandwidth is more than 4 kHz, and the equivalent input noise is less than 1.5 V. The research has perfectly solved the matching problem between high impedance CMOS circuit and low impedance detector.