Studied on the monthly variation of water quality in the Han river between Kwangjang bridge to Nanji island from May to September during 1973. Comparing with the water quality in each area, the concentration of COD and MBAS in Chyeong gae stream and Anyang stream was more higher than that of the Han river. And it was considered that the streams were very polluted for the waste water influence of from Seoul city. Comparing the Han river to upper site(Kwangjang bridge) of it the upper site was not polluted but the Han river was going to polluted for the wastewater influence from Seoul city. In this experiment, the MBAS analytical value was compared statiscally with the value of DO and COD, it showed that there was the relationship between MBAS and DO, COD.