Abstract: The effects of nitrogen and phosphorus on the chlorophyll content of algae inmodel systems of stabilization ponds have been studied in green house during springand summer in 1988 and 1989.When the concentration of TP was all kept constantly at abont 7 mg/L,and that of TN respectively at 13.5,24.8, 44.4 and 77.4mg/L in four experiment series of raw sewage,the increase of chlorophyll content in algae of the sewage was observed with the ratio of TN to TP. The highest chlorophyll content was detected when the TN/TP ratio equals to 77.4/7.01 mg/L, and so was the best result of waste water purification.