Cerium-doped yttrium aluminium garnet (Y3Al5O12, YAG) samples were synthesized by the conventional solid state reaction method. The structure, photoluminescence and thermoluminescence properties were studied. The prepared samples are identified as pure garnet structure by the XRD results. The doping of a small amount of cerium ions has no influence on the structure of the host. Fluorescence spectra show that in the process of the preparation of Y2.95Al5O12 ∶Ce4+0.05 there is self reduction of Ce4+ when calcined in air, Which makes Y2.95Al5O12 ∶Ce4+0.05 emit yellow light peaking at 531 nm when excited by blue light, because a part of Ce4+ have been reduced into Ce3+. Y2.95Al5O12 ∶Ce3+0.05 prepared in weak reducing atmosphere has long yellow afterglow lasting for 35 minutes after it is excited by ultraviolet light. Thermoluminescence measurements show that YAG samples doped with Ce3+ can emit light at higher temperature. There are two obvious thermoluminescence peaks located at 112 ℃ and 256 ℃ in the thermoluminescence curve of Y2.95Al5O12 ∶Ce3+0.05 prepared in weak reducing atmosphore while there is only one located at 128 ℃ in the thermoluminescence curve of Y2.95Al5O12 ∶Ce4+0.05 prepared in air. A conclusion that the thermoluminescence of YAG ∶Ce3+ originates mainly from the Ce3+ trapped by defect energy level can be made out by comparing the cases of doped samples and the un-doped ones.