Using Si3N4 poly-hollow microspheres as pore-forming agent,the porous Si3N4 ceramics were prepared by aqueous gelcasting.The effect of sintering temperature on the properties of the porous Si3N4 ceramics was investigated.The XRD results show that there is only β-Si3N4 phase in the porous Si3N4 ceramics regardless of the sintering temperature.The SEM results show that the Si3N4 poly-hollow microspheres contact with each other and distribute uniformly in the green samples and the porous Si3N4 ceramics.With the increase of the sintering temperature,more and more rod-like β-Si3N4 grains generate in the porous Si3N4 ceramics and the aspect ratio becomes higher and higher,thus the porosity of the porous Si3N4 ceramics decreases,while shrinkage,flexural strength and fracture toughness increase.