Abstract: The forming mechanism of Sm2Zr2O7 prepared by solid reactions using ZrO2 and Sm2O3 as raw materials was studied by FT-IR technology.The results show that the samarium ion entered zirconia crystal and substituted the zirconium ion in order to form ZrO2-Sm2O3 solid solution.Because of the difference in valency,the oxide vacancy was incorporated to maintain the electroneutrality,and the incorporation of oxide vacancy accelerated the forming procedure of fluorite ZrO2-Sm2O3 solid solution.With the raising of temperature,the formed ZrO2-Sm2O3 solid solution transformed gradually into pyrochlore structure Sm2Zr2O7 until forming ideal Sm2Zr2O7 crystal.There was no other phase in the whole procedure.