By　virtue　of　special　heat　effects　of　Spark　Plasma　Sintering　(SPS),　highly　dense　AlN-BN　ceramics　with　φ(BN)=5%-25%　were　fabricated　through　optimizing　the　amount　of　doped　Y2O3.　The　results　indicate　that　increasing　Y2O3　promotes　migration　of　liquid　Y-Al-O　and　formation　of　the　contiguous　liquid　phase.　At　a　high　sintering　temperature,　the　liquid　phase　migrated　to　the　sample　surface　through　their　contiguously　liquid　micro-channels,　and　then　was　removed　through　evaporation,　which　caused　clean　AlN　grain　boundaries.　As　a　result,　thermal　conductivity　of　sintered　AlN-BN　ceramics　was　remarkably　enhanced　compared　with　their　counterparts　with　a　given　Y2O3　content.