In agriculture production, the application of compound fertilizers and phosphate fertilizers bring into the soil large volumes of anions, dominated with phosphate, sulfate and carbonate, which in turn affect selenium availability in the soil to crops. The studies in the past on Selenium adsorption - desorption used to focus on fitting of selenium adsorption with the isotheral equation fitting and effects of single factors on selenium adsorption, and little has been reported on selenium sorption in purple soil and effects of anions on the sorption. Purple soil is the main type of soil in the Sichuan Basin, where neutral purple soil is the highest in area. The study on effects of soil pH and three competitive anions on absorption and desorption of selenium in the purple soil reveals that with increasing soil solution pH, the soil declined in Se adsorption. Selenite adsorption in purple soils varied in the range between 26% to 82% in neutral purple soils, peaked up to 130.1 mol kg^-1, when soil pH was 3, and bottomed to 26% only when soil pH was 9. This shows that soil pH may directly affect the concentration of selenite in soil solution, and hence plant uptake of selenium. With rising soil pH, purple soils reduced their adsorption of selenite, and maximized the adsorption when they were acidic. Effect of HPO₄^2- on selenite adsorption in purple soils was reflected in the finding that selenium adsorption in the soil decreased significantly or by 39.62% when 0.2 mmol L^-1of HPO₄^2- was amended. However, the effect became less significant as more HPO₄^2- was added. Addition of HPO₄^2- into the equilibrium solution significantly reduced soil absorption of selenium, while addition of SO₄^2- did not have much impact on purple soil adsorption of selenium. When 0.3 mmol L^-1 of HCO₄^- was amended, soil adsorption of selenite was significantly increased or by 20.37%, but the effect got to be less significant when more HCO₃^- was added. When 6.5 mmol L^- of HCO₃^-was added, the anion displayed slight competition with selenite. However, addition of a low concentration of HCO₃^- promoted SeO₃^2-absorption by purple soil, while the addition of a high concentration of HCO₃^- acted reversely. The impacts of HPO₄^2- and SO₄^2- on selenium absorption could be well fitted with the Langmuir and Freundlich equations, with coefficient determination R² being over 0.90 for both of them. Selenite desorption rate was significantly higher in the soil solution with HPO₄^2- in presence than in the soil solution without anions in presence, when 0.2 mmol L^-1 and 3.2 mmol L^-1 of HPO₄^2- in presence, selenite desorption rate increased by 2.72 times and 1.50 times, respectively. However, the addition of SO₄^2- did not have much effect on selenite desorption. The presence of HCO₃^-also increased selenite desorption from the soil, and compared with deionized water, it did by 1.41 times and 1.99 times. These findings indicate that desorption of selenite is related to the presence of anions in the extraction solution, and when HPO₄^2- or HCO₃^- is present in the solution selenite desorption rate is significantly increased, but SO₄^2- does not have much effect on desorption of selenite from the soil. Impacts of the three different kinds of anions on Se desorption from the soil vary. The presence of HPO₄^2- or HCO₃^- increases selenium desorption rate, while the presence of SO₄^2- does not have much impact. In the purple soil region, phosphate fertilizer and alkaline ammonium bicarbonate fertilizer are often used. These practices may increase the availability of selenium in the soil, and hence the absorption and accumulation of selenium by plants. The knowledge of the law of purple soil adsorbing and desorbing selenium at the solid-liquid interface may help improve the bioavailability of selenium in the purple soil and serve as a scientific basis for further increasing the content of selenium in agricultural produce.