In　this　paper,　an　iterative　denoising　phase　retrieval　method　is　proposed　to　solve　the　twin-image　problem　in　continuous-wave　terahertz　in-line　digital　holography.　The　iterative　algorithm　is　based　on　the　classical　error　reduction　algorithm　by　adding　the　positive　absorption　constraint　and　a　new　image　denoising　for　the　object　field　to　improve　the　quality　of　the　reconstructed　images.　At　certain　geometrical　parameter,　the　twin-image　can　be　treated　as　noise　superimposed　in　the　object　plane.　The　object　field　is　considered　as　a　complex　function　affected　by　the　twin-image,　and　then　the　denoising　process　embedded　in　each　iteration　is　applied　to　the　real　and　imaginary　parts　of　the　object　field,　respectively.　The　validity　of　this　approach　is　demonstrated　by　the　high-quality　imaging　of　samples　like　the　Siemens　star　and　the　cicada＇s　wing,　which　are　almost　free　from　the　twin-image.　Also,　the　proposed　method　exhibits　good　robustness　to　noises　existing　in　the　hologram,　and　the　reconstructed　images　show　better　quality　compared　with　other　popular　phase　retrieval　methods　and　denoising　algorithm.　This　work　would　be　helpful　to　expand　the　application　of　continuous-wave　terahertz　in-line　digital　holography　in　biomedical　imaging　and　nondestructive　testing.