It is deduced and verified by experiment that the relation between optical intensity and incidence wavefront is nearly linear in unit cell size. Therefore,the formula of PSD sampled by CCD is obtained.According to the formula,many factors affecting the system transfer function in the CCD capture system are simulated and conformed by experiment,such as the maximum spatial frequency of incidence wavefront,the PSD of incidence wavefront in high spatial frequency,the fill factor and the exposure time of CCD. Then some useful qualitative conclusions between these factors and the system transfer function are obtained. Furthermore,the qualitative relation between the exposure time of CCD and repeatability of high spatial resolution interferometric optical test is conformed by experiment.