The assessment of water quality is very important for knowing its suitability for various purposes. Water quality index (WQI) indicates the quality of water in terms of index number for any intended use. It is defined as a rating reflecting the composite influence of different water quality parameters were taken for calculation of water quality index. The water quality of the Al-Sawyer River, which is the main branch of the Euphrates River in the Al-Muthanna Governorate in southern Iraq, was assessed. These study evaluated the water quality using four models of water indices, which are weighted Arithmetic (WA-WQI), Canadian Council of Environment Ministers for the Water Quality Index (CCME), Heavy Metals Index (HPI). as well as Minimum operator index (min). Monthly water samples were collected from three stations on the river from November 2020 to October 2021 and were analyzed, The results of the study showed used the CCME Index to assess the quality of water for drinking, irrigation and living aquatic purposes. And the results were (41.52,Poor) for drinking, ccme for irrigation water value ranged (60.5-93.91, Fair to Good),as well as for aquatic living ranged (Poor –Fair), The results indicated that the river water quality is unsuitable for drinking, but it is suitable for irrigation and aquatic life. WA-WQI Indicator Results showed (237.5, 184.6, 228.6) in three stations respectively, The results of this indices also revealed that the river water is unfit for human consumption. The results indicated that the values of HPI of the three stations were (238.8, 185.5, 230.2) High Polluted in the all stations. The Results WQImin ranged between (Bad to Good water).