Macroporous　silicon　nitride　(Si3N4)　ceramics　with　high　strength,　uniform　structure　and　relatively　high　porosity　were　obtained　by　gelcasting　and　carbonthermal　reaction　in　a　two-step　sintering　technique.　Microstructure　and　composition　were　investigated　by　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM),　X-ray　diffraction　(XRD).　Open　porosity,　pore　size　distribution　and　basic　mechanical　performance　were　measured　by　Archimedes　method,　mercury　intrusion　porosimetry　and　three-point　bending　methods,　respectively.　SEM　and　TEM　results　revealed　that　pores　were　formed　by　elongated　beta-Si3N4.　SADP　measurement　proved　the　formation　of　SiC　particles.　The　SiC　granules　were　beneficial　for　the　formation　of　high　ratio　elongated　beta-Si3N4,　and　at　proper　amount,　they　also　acted　as　reinforcement　phase.　Thermodynamic　analysis　indicated　that　the　mechanisms　of　the　reactions　were　mainly　associated　with　liquid-solid　reaction　and　gas-liquid　reaction.