Abstract: The infrared spectrum,element contents and reaction mechanism of thermal decomposition for cerium propionate crystal were investigated.The results indicated that cerium propionate crystal contained 5 water molecules,the molecular formula for cerium propionate crystal was Ce(CH₃CH₂COO)₃)·5H₂O.The thermal decomposition process for cerium propionate crystal was 4 steps,4 water molecules were lost at 40～95℃,then another water molecule was lost at 100～115℃,one of propionates was lost at 120～230℃ and the cerium(Ⅰ)was oxidized to ceric(Ⅱ)simultaneity,and the remaining 2 propionates were lost at 340～390℃.The final product was ceric dioxide.