A series of samples with the composition Y2.95－xDyxAl5O12:Ce3+0.05(x＝0，0.59，1.18，1.77，2.36，2.95) are prepared by high-temperature solid-phase method. The structure of samples is studied by X-ray powder diffraction method. The results show that crystal lattice of the host expands when Y3+ is substituted by Dy3+, and the expansion is proportional to the amount of Dy3+ which substitutes Y3+. The photoluminescence analysis shows that the substitution results in red shift of emitting peak position and the red shift is also proportional to the value of x. All the samples show yellow long afterglow after they are excited by ultraviolet light. The afterglow time decreases with the value of x. The thermoluminescence analysis shows that there are two kinds of traps with different depths in the host crystal lattice. The substitution of Dy3+ does not change the sorts of traps but it is able to lower the energy level of the traps which is advantageous to the release of electrons in the traps at room temperature.