Vat　photopolymerization　3D　printing　provides　a　novel　approach　for　preparing　broadband　wave-transparent　Si3N4/(3-SiAlON　composite　ceramics.　This　paper　oxidized　raw　powder　to　introduce　low　dielectric　phases　(SiO2)　and　overcome　the　low　curing　depth　of　alpha-Si3N4.　The　solid　content　of　oxidized　alpha-Si3N4　was　increased　to　50　vol%　for　the　first　time　by　modification　with　dispersant.　The　selected　print　thickness　of　50　mu　m　was　the　highest　known　for　Si3N4　vat　photopolymerization　3D　printing,　greatly　improving　printing　efficiency.　Finally,　Si3N4/(3-SiAlON　composite　ceramics　were　sintered　in　the　range　of　1600-1800　degrees　C,　and　the　mechanical　and　dielectric　properties　were　systematically　studied.　The　composite　ceramics　sintering　at　1780　degrees　C　had　a　maximum　bending　strength　of　236　+/-　16　MPa,　and　the　real　permittivity　was　4.83.　At　1800　degrees　C　the　porosity　increased　resulting　in　bending　strength　decreased　to　109　+/-　4　MPa,　and　the　real　permittivity　to　3.23.　This　study　filled　the　gap　in　the　posttreatment　of　oxidized　alpha-Si3N4　and　guided　the　application　of　Si3N4/(3-SiAlON　composite　ceramics　in　the　field　of　wave-transparent.