The corrosion behavior of cerium (Ce) in excess deuterium (D2) was investigated by the pressure-volume-temperature system (PVT) and the hot-stage microscopy (hot-stage microscope, HSM). The phase composition and thermal stability of cerium-deuterium reaction products were investigated by X ray diffraction (XRD) and thermal desorption spectroscopy (TDS). The results show that cerium can quickly react with deuterium to form saturated cerium deuteride (CeD3) at room temperature and the initial deuterium pressure of 43 kPa. After the reaction, the sample is seriously pulverized. A series of cerium deuterides, which have different content of deuterium, can be obtained by heating the saturated cerium deuteride at different temperature. The cerium deuterides have the face-centered cubic (fcc) structure similar to cerium at room temperature. The volume expansion ratio of CeD2 is about 24.3% relative to Ce. However, with the increase of deuterium content, anomalous volume shrinkage of cerium deuteride emerges. Thermal desorption spectrums show that CeD3 could decompose at 120 ℃, but CeD2 could be stable above 600 ℃.