Abstract: We collected water samples at eight sites in the Nanfeihe River from August 2009 to April 2012 every month in order to analyze the temporal and spatial distribution of chlorophyll-a in the river and its correlation with environmental factors. Results showed that the average concentration of Chl.a in the Nanfeihe River was 83.46 g/L, which indicated that the water is highly eutrophic. The concentration of Chl.a significantly increased along with the increase in the concentration of TP, COD, TSS, pH and the water temperature; while decrease along with the increase in SD, -N/TP, the water depth, rainfall and the wind speed. We applied step-wise regression analysis to the data and found that the key environmental factors affecting the concentration of chlorophyll-a were the water temperature, the wind speed, rainfall, and the concentration of TP and -N. By comparing the major impact factors that affect the concentration of Chl.a in the Nanfeihe River and other eutrophic water bodies, we concluded that the water temperature was the most important factor affecting the concentration of Chl.a, In addition, N/P ratio, nutrients, rainfall, wind speed and biological factors were also critical factors.