Terahertz　computed　tomography　makes　use　of　the　penetrability　of　terahertz　radiation　and　obtains　three-dimensional　(3-D)　object　projection　data.　Continuous-wave　terahertz　digital　holographic　tomography　with　a　pyroelectric　array　detector　is　presented.　Compared　with　scanning　terahertz　computed　tomography,　a　pyroelectric　array　detector　can　obtain　a　large　quantity　of　projection　data　in　a　short　time.　To　obtain　a　3-D　image,　in-line　digital　holograms　of　the　object　are　recorded　from　various　directions　and　reconstructed　to　obtain　two-dimensional　(2-D)　projection　data;　then　2-D　cross-sectional　images　and　3-D　images　of　the　internal　structure　of　the　object　are　obtained　by　the　filtered　back　projection　algorithm.　The　presented　system　can　rapidly　reconstruct　the　3-D　object　and　reveals　the　internal　3-D　structure　of　the　object.　A　3-D　reconstruction　of　a　polyethylene　straw　is　presented　with　a　6%　error　in　retrieved　diameter.　(C)　2016　Society　of　Photo-Optical　Instrumentation　Engineers　(SPIE)