An experiment was carried out to evaluate effects of nutrient salts with different phosphorus concentrations on the growth of Scenedesmus obliqnus and the chemical compositions in it. In this study, six groups of culture solution with different initial concentrations (0.0054, 0.054, 0.54, 2.7, 5.4 and 8.1 mg / L respectively) were prepared, and the non-phosphorus BG11 culture solution was used as the blank control group. The results showed that the cell density, dry weight and growth rate increased with the increase of phosphorus concentration; the optimum concentration range of phosphorus is 5.4 ~ 8.1 mg / L for the growth of Scenedesmus obliqnus; the growth limiting effect of phosphorus on Scenedesmus obliqnus was detected under the concentrations ranged from 0.0054 to 0.054 mg/L; the volume of individual cell increased significantly when the phosphorus concentration is limited; the contents of C, N and P in Scenedesmus obliqnus increased with the increase of phosphorus concentration; there is a slight difference between the ratio between the contents of C and N in Scenedesmus obliqnus, which ranged from 11:1 to 14:1 under various phosphorus concentrations; and tthe ratio between the contents of C and P and the ratio between the contents of N and P decreased sharply with the increase of phosphorus concentration; It is concluded that different phosphorus concentrations have significant effects on the growth of Scenedesmus obliqnus and the chemical composition in it.