The present study was conducted to calculate the ecological amplitude of nitrate and to obtain the optimum nitrate concentrations, optimum growth, and tolerance range of nitrate concentrations during the growth of Scendesmus obliquus. Three fixed initial phosphate concentrations 0.02 mg/L (low-P), 0.2 mg/L (medium-P) and 0.4 mg/L (high-P) were carried out based on the surface water environmental quality standard of the People's Republic of China. A nitrate tolerance model of the algal growth was established based on the Shelford's law of tolerance. The results showed that the optimum nitrate concentrations in low-P, medium-P, and high-P cultures were 1.02, 8.91 and 18.05 mg/L, respectively; the optimum growth range of nitrate concentrations were (0.1420.006), (0.3140.002) and 0.3460.007/d, respectively; the tolerance range of nitrate concentrations were (0.022.02), (0.0517.77) and 5.3930.71 mg/L, respectively. These results suggest that water pollution may promote the growth and production of Scendesmus obliquus, and Scendesmus obliquus may be a good indicator for the high nitrogen water environment.