Uranium-doped YAG powder was first synthesized via a co-precipitation method. Pure-phase powder with a oxidiation state of U4+ was obtained by calcinating the precursor in reducing atmosphere. Divalent calcium ions were introduced to balance the extra charge from the substitution of U4+ for Y3+ in YAG. The synthesized monophase powder could be used to fabricate transparnet ceramics for the use in laser applications.