An investigation is reported by the coating of BaMgAl10O17:Eu2+ phosphor by aluminum oxide using atomic layer deposition. Aluminum oxide films were prepared the chamber temperature of 350 degrees C using Al(CH3)(3) and H2O as precursors and reactant gas, respectively. EDX and FTIR analysis showed the surface composition of coated phosphor was aluminum oxide. The photoluminescence intensity of coated phosphors showed 10.3 similar to 36% higher than that of uncoated. This means that the reactive surface is uniformly coated with stable aluminum oxide to reduce the dead surface layer without change of bulk properties.