Based　on　the　diffraction　propagation　mechanism　of　terahertz　waves　and　the　basic　theory　of　binary　optics,　transmission　terahertz　Dammann　gratings　is　designed,　fabricated,　and　characterized　for　the　working　wavelength　of　2.52THz.　The　simulated　annealing　algorithm　is　used　to　design　the　phase　structure　of　a　2D　terahertz　Dammann　gratings　which　can　generate　2×2　and　6×6　diffraction　beams.　MATLAB　is　used　to　conduct　diffraction　beam　splitting　simulation　of　the　designed　Dammann　grating.　The　simulation　results　show　that　the　2D　diffraction　efficiency　of　the　grating　reaches　around　60　%,　and　the　unevenness　of　the　split　sub-spots　is　controlled　below　1%.　During　the　grating　fabrication　process,　N-type　high-resistivity　silicon　(n　=　3.4175　@　2.52　THz)　is　used　as　the　grating　material,　and　silicon　nitride　(Si3N4)　with　200nm　thickness　is　used　as　the　hard　mask　layer.　To　achieve　extremely　high　etching　depths,　the　wet　deep　silicon　etching　process　of　potassium　hydroxide　(KOH)　solution　is　used　as　the　fabrication　process.　Various　pivotal　process　parameters,　such　as　the　initial　concentration　of　each　component,　are　optimized　through　many　experiments.　The　etching　depth　of　the　order　of　50　μm　is　achieved.　The　grating　surface　flatness　and　step　sidewall　steepness　satisfy　the　needs　of　use.　The　characterization　experiment　results　show　that　the　2D　diffraction　efficiency　of　the　grating　is　about　50　%,　and　the　unevenness　is　about　2.5　%,　which　basically　verifies　the　reliability　of　the　design　theory　and　fabrication　process.　©　2022　SPIE.