Abstract: To explore the water quality response and the change rule of the South-to-North Water Transfer Project and the Project of Yellow River to Qingdao City in the water delivery section of the pilot trench of the Xiaoqing River under the multi-source water transfer scheme of the diversion of the Yellow River water and Yangtze River water,and to find the best water quality and water distribution scheme under the current water transfer capacity,this paper takes dissolved oxygen,permanganate index,COD,BOD₅,ammonia nitrogen,total nitrogen,to‐tal phosphorus,and fluoride as research indexes and studies the water quality optimization scheme of multi-source water transfer during wa‐ter delivery period,hoping to provide a theoretical basis for water transfer management in the research area.First of all,11 monitoring points were set to monitor the water quality during the water transfer period.The measured water quality data and the design materials of the research area were taken as the basic data,the MIKE11 hydrodynamic-water quality coupling model was constructed and calibrated from the flood diversion gate to the section of the lower check gate.Then,the upstream section of the Dongqing Expressway was taken as the assess‐ment section,the flow rate of the lower check gate of 36m~3/s was taken as the control condition to set 99 kinds of water distribution scenarios,and the changes in water quality indexes in the simulation results under different water distribution schemes were summarized and analyzed.In the end,the water pollution index method was adopted to assess the water quality simulation results and the best water distribution scheme was determined.The conclusions are as follows:the total nitrogen content in the research canal section was relatively high,the other indexes met the class III water standards,the dissolved oxygen,permanganate index,COD,and fluoride in the water source of the Yangtze River were relatively high,and the BOD₅,ammonia nitrogen,total nitrogen,total phosphorus content in the water source of the Yellow River were relatively high.The efficiency coefficient Ens of the flow in the hydrodynamic-water quality coupling model was 0.86,the determination coef‐ficient R~2 was 0.88,the error of the water quality simulation results was within 30%,and the effect of the model simulation was good.With the constant improvement of the contribution rate of the Yangtze River water to the water transfer,the fluoride,dissolved oxygen,and permanganate indexes in the water after the catchment showed an upward trend,and the COD first decreased and then increased,the other indexes showed a downward trend.The contents of most pollutants had a linear relationship with the contribution rate of the Yangtze River water,the difference in water quality between the two water sources had a relatively great influence on the water quality of the catchment,and the water environment had a relatively small effect on the decomposition and diffusion of pollutants.In various simulation scenarios,the COD and BOD~5 at the assessment section （the upstream section of the Dongqing Expressway） played a decisive role in the WPI of this section.When the water supply of the Yangtze River accounted for 49% of the total water supply （17.64 m~3/s）,the WPI of this section reached the minimum value （51.17）.Therefore,this scheme is the best water distribution scheme obtained by the research.