In order to design and optimize the optical system of digital holography, rebuild the object field with high quality, the characteristics of imaging system with spherical and plane reference wave are demonstrated respectively based on optical scalar diffraction theory. Based on the discrete Fresnel diffraction integral, recording and reconstruction of hologram with plane reference wave as well as the impact of CCD size and reconstructed distance on holographic imaging have been simulated with matlab. The simulation results show that: zero-order image and twin images are spatially separated when choosing the parameters of recording system properly; the quality of rebuild image suffers as CCD decreases in size and the reconstruction distance deviates from the recording distance. © 2018 SPIE.