Abstract: In this paper, the cultivation of Spirulina Platensis was enhanced by Na2SeO3 addition in the medium. Some factors such as Se(IV)concentration, sulphite and Se bioaccumulation as well as its effect on the algal cell molecular functional group structure etc. were investigated in detail. In addition, the relevant mechanisms were discussed. It was found that Se(IV)had both stimulation inhibition effects on the culture of Spirulina platensis. Within the concentration range of 0.02mg/L—411.00mg/L, Se(IV)not only can stimulate the growth speed of Spirulina platensis, but also can improve its biomass yield. Se bioaccumulation in Spirulina platensis will rise up with the increase of Se(IV)concentration and will beneffit from the algal slow growth. The toxicity of higher concentration selenite on the growth of Spirulina platensis could be decreased by sulphite addition. There is no damage to the molecular functional group structure of Spirulina platensis during Se-enrichment culture. On the basis of this study, the appropriate Se(IV)concentration range for Spirulina platensis cultivation is about 10mg/L—40mg/L.