We measured the total selenium content in aquatic product samples after oxidation of organic selenium into inorganic selenium using a nitric acid, perhydrol mixed system. Simultaneously, we measuredinorganic selenium content by HG-AFS following extraction of the sample in a HCL(50%) solution and digestion of the water phase in HNO₃ and H₂O₂. Using these data we calculated the organic selenium content of the samples. Under optimal conditions, the detection limit of selenium by this method was 7.1 ng/mL and the linear range was between 0–20 μg/L. The recovery rate of total selenium was 93.88%–107.65% and the RSD was 0.82%­­­­­–4.97%. Similarly, the recovery rate of organic selenium was 82.88%–90.10% and the RSD was 2.33%–7.73%. In summary, this method has a wide linear dynamic range and good precision and accuracy, so is suitable for the determination of organic and inorganic selenium in aquatic products.