This paper describes a low-noise front-end readout circuit for CZT detectors based on TSMC 0.35 um mixed-single CMOS technology; mainly analyzes the noise model of the detector-preamplifier and presents the low-noise circuit schematic of charge sensitive preamplifier and shaper. Considering the parasitical influences, the circuit and layout-design are optimized to reduce noise. The preliminary simulation results show that, the equivalent noise charge (ENC) is 74 e^﹣ (rms), noise slope is 9 e^﹣/pF, power consumption is 2 mW, and non-linearity is <3%.