Abstract: Coal ash containing higher than usual selenium has a comprehensive utilization value. Although selenium in coal ash samples has been studied in some areas, there is no formed reliable method to determine the selenium content in coal ash due to the complex matrix. In the paper, referring to the analysis of coal and soil samples, a method to determine selenium in coal ash by Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS) is described. The samples were first digested by microwave digestion in HF+HNO₃+H₂O₂ without other pretreatment. The obtained clear and transparent digestion solution was reduced by 30％ HCl. The interferences of coexisting elements were eliminated by adding Fe(Ⅲ) salt without interference with Se. The detection limit was 0.020 μg/g. The relative standard deviation was less than 4.2% (n=5). Recoveries of samples were in the range of 94.0%-105.0%. The method has been validated by analysis of standard reference coal fly ash and the analytical results are in agreement with certified values, which indicates that it is a feasible method to detect Se in coal ash.