Abstract: The application of N₂O-C₂H₂ flame Atomic absorption spectrometer to measure of silicon in the alloy expands is studied.This paper introduces the optimum measuring conditions for silicon and potency in which a fine liner range presents.And makes a synthetic consideration to interference factors.The method has the advantages of high sensitivity,less interference and good in selectivity and reappearance.The relative standard deviations are all less than 1.0%(n=6)in six sample measures,and the standard adding recovery is in the range of 97.0%～99.0%(n=6),the practice shows that the method is fully suitable to measure the silicon in the alloy expands.