Abstract: With two different sample decomposition methods of conventional wet digestion and microwave high pressure dissolution method, the determination of Se in chimney ash by HG-AFS is studied. Se standard concentration has good linear relationship with fluorescence intensity in the range of 0.000~0.024 mg/L,and corelative coefficient is 0.999 8. Detection limit of the method is 0.007 5 mg/kg, relative standard deviation is between 0.87%~1.30%,and recovery is 98%~105%.This method has the advcontages of high sensitivity,rapidity and accuracy.It provides scientific basis for recycling use of selenium in chimney ash.