To capture the space-borne remote sensing aerosol data with high signal-to-noise ratio (SNR), according to the chain of the imaging system, the main factors on the SNR of spectrometer were presented. Combined with the imaging system response model and the expression of SNR, a modular design method for high SNR of spectrometer imaging circuit system was proposed for visible detectors and infrared detectors. From the overall design to the module design of Cloud and Aerosol Polarization Imager (CAPI) imaging circuit development plan was described. The radiation calibration experimental results indicate that the minimum SNR of visible channel image under typical radiance conditions is 50.9 dB, the minimum SNR of infrared channel image under typical radiance conditions is 62.3 dB. The design method of visible detectors and infrared detectors provides references for other spectrometer imaging circuit system in remote sensing fields.