Abstract: 100 μL of mouse plasma sample was added into the digestion tank, and 5 mL of nitric acid and 2 mL of 30% (w) hydrogen peroxide solution were added for microwave sealed digestion. After cooling, the sample solution was treated to volatilize acid to less than 0.5 mL, and then diluted to 25 mL with water. ⁷³Ge was used as the internal standard and the standard detection mode (STD) was selected. The linear range of selenium was 0.2-20 μg·L^-1, and the detection limit (3s) was 6.75 μg·L^-1. Values of recovery obtained by standard addition method were between 93.1% and 105%, and the relative standard deviation (n=6) of the measured values was less than 5.0%. The method was used to determine the selenium content in the plasma of selenium supplemented mice, and results showed that the selenium content changed with the administration time.