This paper discusses the results of studies on the use of BOD5, COD and DO as indices of oxygen-consuming organic matter in measuring the BOD5, COD and DO content of the Haihe River estuary area in the Bohai Bay, and on their distributional patterns. The diurnal variation of COD content is related to salinity and water depth, but is mainly influenced by tidal effects. The BOD5/COD ratio is 79% in the Yongdingxing River, 160% in the southern sewage discharge river, 30% in the estuary. The biological and chemical degradation rate of oxygen-consuming organic matter in the Yongdingxing River and in the southern sewage discharge river is rather high. The selfpurification factor of BOD5 and COD in the Yongdingxing River is 0.163 and 0.038.