A　key　requirement　to　put　terahertz　(THz)　imaging　systems　into　applications　is　high　resolution.　Based　on　a　self-developed　THz　quantum　cascade　laser　(QCL),　we　demonstrate　a　THz　inline　digital　holography　imaging　system　with　high　lateral　resolution.　In　our　case,　the　lateral　resolution　of　this　holography　imaging　system　is　pushed　to　about　70　mu　m,　which　is　close　to　the　intrinsic　resolution　limit　of　this　system.　To　the　best　of　our　knowledge,　this　is　much　smaller　than　what　has　been　reported　up　to　now.　This　is　attributed　to　a　series　of　improvements,　such　as　shortening　the　QCL　wavelength,　increasing　Nx　and　Ny　by　the　synthetic　aperture　method,　smoothing　the　source　beam　profile,　and　diminishing　vibration　due　to　the　cryorefrigeration　device.　This　kind　of　holography　system　with　a　resolution　smaller　than　100　mu　m　opens　the　door　for　many　imaging　experiments.　It　will　turn　the　THz　imaging　systems　into　applications.　(c)　2017　Society　of　Photo-Optical　Instrumentation　Engineers　(SPIE)