Abstract: In order to improve the imaging quality of pre-magnification digital holography, the imaging systems of pre-magnification digital holography with the plane wave and spherical wave respectively as the reference light are studied and compared theoretically and experimentally. The results show that, the lateral resolution of the two systems mainly depends on the resolution of microscopic lens in general experimental conditions. When the recording distance is short, the lateral resolution of both systems will be slightly lower with the recording distance increasing; and when the recording distance is comparatively large, the resolution of the system with spherical wave as the reference light is worse, scilicet, the system of plane wave is relatively superior. As the recording distance of the hologram is zero, which is named as digital image-plane holography, the resolution of reconstructed image is best. When an ordinary industrial sensor is adopted, the lateral resolution far exceeds 2.19 m, and the image quality is fairly good. Reducing the recording distance of digital hologram as much as possible, or employing the digital image-plane holography, can improve the imaging resolution of digital holography.