Abstract: In order to study the impact of pollutants transporting of Kherlen River to the water quality of Hulun Lake， taking Kherlen River as the research object，the paper monitored ammonia nitrogen，total nitrogen，total phosphorus and chemical oxygen demand( COD) ，analyzed the main reason for the changes of the water quality of Kherlen River and the correlation between the indexes，and used the water pollution index method to determine the main pollution factors in the water． The results showed that the water quality of all monitoring sections in Kherlen River were inferior grade class V and the main pollutants were total nitrogen and COD． Ammonia nitrogen and total nitrogen in water were extremely significant positive correlation，and the correlation coefficient was 0. 850． Also there was significant positive correlation between COD and total phosphorus， and the correlation coefficient was 0. 691． The constant input of nitrogen，phosphorus and organic compounds increased the eutrophication degree of water body in Hulun Lake．