Large-scale　autostereoscopic　three-dimensional　(3D)　light-emitting-diode　(LED)　displays　can　provide　high-quality,　even　immersive,　visual　experiences.　However,　the　unique　structural　characteristics　of　the　LED　display　panel　can　enhance　moiré　effects　during　parallax　generation.　We　present　a　novel　method　for　quantitatively　characterizing　the　moiré　effect　in　autostereoscopic　3D-LED　displays　using　a　model　applying　geometrical　ray　tracing　and　a　brightness　distribution　stack.　An　optical　diffuser　(OD)　device　for　moiré　reduction　and　performance　balance　is　designed　and　the　influence　of　several　key　device　parameters　on　moiré　pattern　features　are　examined　in　autostereoscopic　3D-LED　displays　for　the　first　time.　Using　the　obtained　optimal　parameters,　we　assembled　an　ultra-large　moiré-less　autostereoscopic　3D-LED　display　prototype,　which　was　experimentally　shown　to　be　capable　of　reducing　moiré　fringes　without　noticeable　increase　in　crosstalk　or　significant　reduction　in　visual　quality.　Finally,　the　effects　on　the　moiré　and　crosstalk　effect　of　altering　key　influencing　factors　were　examined.　©　2019　Optical　Society　of　America　under　the　terms　of　the　OSA　Open　Access　Publishing　Agreement