Resolution of digital holographic microscopy was theoretically and experimentally researched.Three important conclusions are achieved:1) By analyzing the demand for spatial resolution of recording medium in different digital holographic recording setups,it shows that lensless Fourier transform holography can relax the requirement of spatial resolution and use the full spatial bandwidth of the CCD sensor.2) Because of the differences of spatial resolution of image planes in different directions,reconstructed images can be relatively extended in the direction of high spatial resolution and reduced in the direction of the low one.3) Lateral resolution of the reconstructed images is mainly determined by the highest spatial frequency of digital holograms recorded by CCD,and increases with the larger CCD size,the higher spatial resolution of the CCD sensor,and the shorter recording distance.Furthermore,the method and experimental results of eliminating the aberration of reconstructed images were presented,and three approaches to increase the lateral resolution of the reconstructed images were investigated.