A method for the determination of organic and inorganic selenium in purple sweet potato by hydride generation-atomic fluorescence spectrometry(HG-AFS) had been presented.The effects of the instrumental parameters,chemical parameters and interferential elements on atomic fluorescence signal of selenium were investigated.The contents and ratio of organic and inorganic selenium in different extraction methods were compared.The detection limit for selenium was 0.019 ng /ml under the optimum conditions.The linear range was 0～100 ng/ml.The relative standard derivation was 1.34 %.The recoveries were 105.2%～107.1%.The organic selenium content was(36.80 ±0.51) ng/g in purple sweet potato,which is above 56% of the total selenium.