In this paper, the determination of Ba using oxygen enriched air-acetylene flame in AAS has been studied and the effect of acetylene flow, oxygen flow and the ratio of O2/C2H2 on the absorbance have been compared. When the amount of oxygen is 52% in mixed gas and the ratio of O2/C2H2 is about 0.72, higher sensitivity for Ba can be obtained. In this flame acids and most of elements did not interfere. By adding 1,000 mg.L-1 K the interference can be minimized and the sensitivity for the determination of Ba can be increased. The sensitivity of the method is 0.16 mg.L-1/1%, the detection limit is 0.034 mg.L-1, and the relative standard deviation is 2.5%. The analytical results of the standard reference material (GBW08301 and GSD-6) by this method are consistent with the certified values, and it was proved that this method are reliable and is suitable for the determination of Ba in mineral water.