[Objective] The water quality of four monitoring sections of the main stream of the Beiluo River from 2014 to 2020 were evaluated and analyzed in order to provide a basis for further improving the water environment of the river basin.[Methods] The main pollution indicators of the Beiluo River were screened and evaluated using principal component analysis and a comprehensive water quality identification index method according to the law of intra-annual distribution of water volume in the Beiluo River. A given year was divided into the wet season

the flat water season

and the dry season.[Results] Chemical oxygen demand

ammonia nitrogen

and fluoride were the most significant indicators affecting the water quality of the Beiluo River. From the distribution along the course of the river

the water quality in middle reaches of the main stream of Beiluo River was the best

followed by the upper reaches. The water quality in the lower reaches was relatively poor. The water quality in the main stream of the Beiluo River improved significantly after 2018

basically meeting the requirements of water functional area Ⅲ water quality.[Conclusion] The main source of pollution in the upstream and midstream sections of Beiluo River came from the discharge of domestic sewage and livestock breeding wastewater from coastal towns. Industrial wastewater from the coal chemical industry and other enterprises in the downstream section of the river and agricultural surface source pollution caused by nitrogen fertilizer application were the main factors affecting the water quality of the river.