Abstract: The hydrogen isotopes behavior of lithium ceramic tritium breeders was considered as an important issue of the tritium breeding blanket in a fusion reactor. The chemical states and the deuterium desorption behavior of Li₄SiO₄ implanted with 3 keV D⁺ were investigated by the in-situ X-ray photoelectron spectroscopy (XPS) and the thermal desorption spectroscopy (TDS). It is found that deuterium implantation changes the chemical states on the surface of Li₄SiO₄, and produces many defects and binding groups. The deuterium retention and the desorption behavior are influenced significantly by the sample temperature at the time of implantation, which can speculate the tritium retention behavior in the tritium breeder blanket.