By means of co-precipitation, pure YAG phase was synthesized from the reaction of aluminum yttrium and cerium nitrates with ammonia as precipitator. In order to obtain the special coating oxide precursor, the metal ions solution and ammonia were respectively added with fixed ratio by two peristaltic pumps to maintain an expired pH value and reaction rate. The as-received precursor was annealed at 700°C and 900°C respectively. The structure, phase evolution and morphology of the as-prepared YAG nanopowders were tested by XRD, BET and SEM. At lower temperature (900°C), coating oxide precursor was directly transformed to nanopowders of pure YAG phase. The high salt solution concentration was critical for the control of chemical homogeneity within the precursors. The YAG nanopowders were less-aggregated and better-dispersed. The luminescent properties were examined and discussed.