应用溶胶－凝胶方法合成了ＹＳＺ（Ｚｒ０２＋９ｍｏｌ％Ｙ３Ｏ３）超细粉末。对凝胶形成超细粉末的热分解及晶化过程用ｘ射线衍射（ＸＲＤ）和热重一差热（ＴＧ－ＤＴＡ）等分析方法进行了研究。试验表明，溶胶一凝胶法制备ＹＳＺ超细粉末的反应过程分为：水份和有机溶剂的挥发；有机基团的燃烧和无定形Ｚｒ０２的形成；无定形Ｚｒ０２向立方相Ｚｒ０２的转变三个阶段。在４７０℃时，凝胶转变为ＹＳＺ固溶体，形成立方相Ｚｒ０２结构。 YSZ (ZrO2 + 9mol% Y3O3) ultrafine powders were synthesized by sol-gel method. The thermal decomposition and crystallization of the ultrafine gel powder were studied by X-ray diffraction (XRD) and differential thermal analysis (TG-DTA). The experimental results show that the reaction process of YSZ ultrafine powder prepared by sol-gel method is divided into: the evaporation of water and organic solvents; the combustion of organic groups and the formation of amorphous ZrO2; the transformation of amorphous ZrO2 to cubic ZrO2 three stage. At 470 ℃, the gel transformed into YSZ solid solution to form cubic Zr02 structure.