Abstract: The application of nitrous oxide-acetylene flame atomic absorbance spectral method to measure the content of calcium in positive powder of thermal activated batteries is studied. The optimum measuring conditions for calcium and potency in which a fine liner range presents, and makes a comprehensive consideration to interference factors was introduced. The method has the advantages of high sensitivity,simple operation, easy master, short analyzing cycle, less interference and good in selectivity and repeatability. The relative standard deviations are all less than 1.0% in ten sample measures, and the standard adding recovery is in the range of 97%～102%. The practice shows that the method is fully suited to measure the cadmium content in positive powder of thermal activated batteries. The proposed method was proved to be a useful instrument analytical technique in nitrous oxide-acetylene flame absorbing spectral method.