The Air-acetylene Flame Atomic Absorption Spectrometry (FAAS) was used to measure Sr content in Mg-Sr Alloys. The experiment conditions including acetylene flow rate, measurement height, flame wavelength were studied and the disturbing factors were discussed. It was found that, as dissolution agent of alloys and LaCl3 as the deionization agent and flame wavelength being 460.7nm, the detection limits is 1.16mg/L and the relative standard deviations is less than 0.3% and the recovery rates of Sr is more than 95%. The advantages of this method were summarized as: high sensitivity and precision, low chemistry disruption, good selectivity, good recurrence characteristics of the measuring conditions. The method is suitable for the control analysis and sample-system analysis of determination Sr content in the Mg-Sr Master Alloys.