Abstract: By analyzing the monitoring data on the prime pollutants in the province-control sections of Songhua Lake from 1989 to 1997,it is found that the variation of the nourishment salts is very great in the water.The existence of nourishment salts causes the pollution of Songhua Lake.The investigation and detection results show that different gradient and different ground cover are main factors affecting the variation of nourishment material in the water in terms of same rainfall and other conditions.