According　to　optical　imaging　theory　and　the　point　spread　function　of　digital　holographic　system,　the　imaging　resolution　of　the　digital　holographic　microscopy　was　investigated.　The　imaging　resolution　expressions　of　the　digital　holographic　Systems　with　and　without　pre-magnification　were　presented　in　details.　With　those　formulas,　it　is　clearly　shown　that　only　when　the　imaging　resolution　of　CCD　is　not　below　the　resolution　of　the　microscope　objective　(MO),　the　imaging　resolution　of　the　whole　system　is　dependent　on　the　numerical　aperture　(NA)　of　MO.　Otherwise,　it　is　dependent　on　the　numerical　aperture　of　the　CCD.　Experimental　imaging　of　US　air　force-resolution　test　target　is　performed　using　the　lensless　Fourier　transform　configuration.　The　experimental　results　that　ultimate　resolution　of　reconstructed　image　in　horizontal　direction　and　vertical　direction　is　3.91　μm　and　4.38　μm　respectively.　Finally,　recording　and　reconstructing　of　holograms　for　stripe　object　are　stimulated,　and　results　are　corresponding　with　theoretical　analysis.