Abstract: UO₂ fuel kernels were preparaed by gel-casting method. When the slurry was dispersed into a hot organic liquid, the slurry drops would become micro-spheres with the surface tension, and organic monomers in the slurry would be polymerized in the initiating of high temperature, as a result, U₃O₈ green micro-spheres would be produced. The advantages of putting catalyst into organic oil is that the slurry can be kept long time for the dropping, and the temperature of organic oil could be decreased with the increaseof catalyst content. When 1.5% (in volume) catalyst is dispersed in the dimethicone, the gelation temperature is 50 ℃.