To access the water quality of upper Abbay River using modified Streeter & Phelps modeling, water samples were collected from four stations at River (at Cherechera weir(dump),around textile factory effluent mix to Abbay River, around Bahir dar tannery effluent mix to Abbay River and seen one site below all pollutant sites to observe dilution factor of our overall study area and two effluent sample points (at textile and tannery factory effluent). Water samples collected from these stations were taken for laboratory analysis for BOD, COD, DO, TDS, turbidity, Electrical conductivity, Temperature and pH. The results of the analysis showed that the P H which ranged from 7.14 to 7.98 which are fulfill with WHO and EPA standard limit. The temperature values around Bahir dar textile factory effluent and around Bahir dar tannery effluent mix with river Abbay records relatively higher due to entry of waste water effluent. The COD values Around Bahir dar tannery effluent mix with Abbay River is above the standard limits of WHO and EPA while all of TDS values are within WHO and EPA the standard limits. The BOD values 27mg/l to 64mg/l most stations were higher than the set 30mg/l standard limits of WHO. The de-oxygenation constant �d and ultimate BOD Lco gave 1.235 and 27 mg/l respectively. The re-aeration constant Kr, gave 1.075. The minimum DO level of the River was11.28mg/l. From the measured and simulated DO showed that there was minimum DO around the effluent discharge due to excesses in COD, BOD,TDS and turbidity deposits. Keywords modified of Streeter-Phelps model, Dissolved oxygen, Biochemical oxygen demand, Abbay River, re-aeration, de-oxygenation.