Terahertz　digital　holography　is　a　non-scanning　and　real　time　method　for　reconstructing　the　absorption　and　phase　distributions　of　the　wave-front　diffracted　by　a　given　sample　simultaneously　in　the　terahertz　region.　A　continuous-wave　terahertz　in-line　digital　holographic　multi-plane　imaging　method　is　presented　here　for　achieving　a　three-dimensional　shape　of　a　specific　portion　of　a　sample　with　the　best　possible　focus.　The　three　enhancement　techniques　of　synthetic　aperture,　autofocusing　and　phase　retrieval　are　applied　to　the　single　plane　recordings　for　achieving　a　high　resolution,　good　quality　and　optimally　focused　reconstructed　image.　Later,　multi-plane　reconstructed　images　are　processed　with　the　threshold　mask　and　a　three　dimensional　profile　of　the　sample　is　obtained.　Experimental　verification　confirms　that　the　proposed　method　is　a　valid　tool　for　acquiring　multi-plane　information　of　a　target　in　the　terahertz　range.