Abstract: Scientific and objective evaluation of water quality is a prerequisite for water resources management.The currently applied water quality evaluation methods have problems such as poor combination of qualitative and quantitative evaluation,inconsistent evaluation results with legal standards,complex calculation processes,and unintuitive evaluation results.It is necessary to develop a more scientific and practical evaluation method.Based on the advantages of the widely used evaluation methods,such as single factor evaluation method,Water Pollution Index(WPI)method and water quality identification index method,the Water Quality Level Index(WLI)method was designed and improved in this article,and the Water Quality constituent concentrations were standardized by de-dimension treatment.The results showed that the WLI method truly realized the quantitative and continuous analysis of water quality.With this method,the water quality index comparison analysis,time change trend analysis and spatial variation analysis can be effectively carried out.The method has been well applied in water quality assessment,early warning and water quality monthly(special)report preparation in coastal areas of southern Guangxi.It was proved that this method is simple and easy to implement,and has certain promotion value.