Based on Si powder,SiC grains and powder as the raw materials,Si3N4-bonded SiC standard bricks were prepared by reactive sintering (at maximum 1 420 ℃) through the same processes,which were then post-sintered at 1 750 ℃ for 2.5 hours in flowing N2 atmosphere. The phase compositions,micro-zone compositions,microstructure as well as pore-size distribution of Si3N4-bonded SiC samples before and after post-sintering were analyzed by means of XRD,EDS,SEM and mercury intrusion method respectively.The results showed that after post-sintering at high temperature,the Si3N4-bonded SiC refractories,in which fibrous Si3N4 disappeared and all α-Si3N4 were transformed to relatively large-sized columnar β-Si3N4,presented almost no dimensional change,only a little decrease of bulk density and a little increase of MOR and HMOR （1 400 ℃)；the average pore-size increased dramatically；the steam oxidation resistance at high temperature was also enhanced remarkably.