In the Fourier transform spectrum detection technology of atmospheric composition and content detection, the output current signal of infrared detector is generally very weak. In this paper, a multi-channel weak current signal high-precision acquisition circuit is designed by analyzing the source of system noise, using high-precision and low-noise integrated operational amplifier, and reasonably selecting circuit parameters. An analysis of the circuit performance shows that the system can accurately acquire the nA level 1kHz current signal, and meet the requirements of weak signal detection.