The novel static polarization wind imaging interferometer adopts four-face pyramid prism and polarization array to obtain four different phase interferograms on four sections of CCD once. It can detect the target in real time and overcome the moving mirror scan detection mode defect that leads to be unable to accurately detect the rapily changing target. For the signal beam that is split into four equal parts, their intensities drop significantly, so whether the signal can be detected is a key problem. In this paper, the target spectral characteristic of the airglow is taken as the starting point of analysis, then the optical transmission properties and response of the NSPWII system and CCD signal-to-noise ratio are analyzed. Finally the conclusion is obtained that weak signal (such as night airglow) cannot be detected in the conventional detecting mode. Some improving measure is presented which extends light integration time, adopts pixel merger technology and select high sensitivity CCD (as electron multiplication CCD), they all can improve the signal-to-noise ratio effectively. After integrated using the these measures, the signal-to-noise ratio and responsiveness of NSPWII system are calculated. In view of the rapid changes of cost and objectives, only pixel binning is adopted, and the simulated curve of signal-to-noise ratio versus digital output is obtained. The result shows that the weak signal as night airglow can be detected.