A new technique for the fabrication of yttria stabilized zirconia (YSZ) substrates using aqueous gel-casting has been developed. This technique has been used to fabricate planar thin-substrate YSZ fuel cells. A thin-substrate YSZ electrolyte with high density and low porosity was prepared by this method with 57vol% solid content slurry. The character of the technique was discussed based on the influence of dispersant and pH value on slurry. After sintering, the YSZ electrolyte thickness is between 100 and 200µm, and the electrolyte area is 100 × 100 mm2. The research shows that aqueous gel-casting allows fabricate thin YSZ substrate with high density and homogenous structure. The method is suitable for preparing thin-substrate electrolyte of yttria stabilized zirconia.