Charge coupled device (CCD) is a key component in a remote sensing system. In order to obtain high signal-to-noise ratio (SNR) and dynamic range in low illumination and quantization circumstance, first, according to CCD architecture and noise physical characteristics, relationship between analog gain quantization step and CCD SNR is proposed; next, integrating sphere calibration system is established, shot noise, photo response nonuniformity and noise floor model are also built, and the next relationship between analog gain and SNR in low illumination condition is analyzed thoroughly; finally, the practical photographing system is built, and remote images in different gain parameters are acquired. Theoretical analysis, experimental calibration, and practical images all indicate that when analog gain is increased by one to two times, the SNR is improved greatly and dynamic range is acceptable.