Porous Si3N4 ceramics were fabricated through a novel gelcasting method followed by pressureless sintering.Water-soluble copolymer of isobuthylene and maleic anhydrade(Commercially called Isobam)was used as a dispersant and gelling agent,the Si3N4 slurry with 0.2wt%Isobam was favorable to form a fine homogeneous green body in air at room temperature.Rheological measurement results revealed that all slurries showed the distinction of shear-thinning at low shear rates.