Abstract: Water allocation of the Yellow River basin (YRB) after the first phase of South-to-North Water Diversion Western Route Project (WRP) takes effect will determine the rebuilding of water resources allocation framework of YRB and the evaluation of economic benefits of water supply of WRP, and support technologically the construction of the national water network. Given that WRP covers the main water supply areas of YRB, water diversion of WRP shall be allocated conjunctively with water resources of YRB. A hierarchical water allocation model, which gives first priority to ecology, followed by equity and efficiency, are constructed, and water diversion of WRP is allocated based on balanced provision. Water allocation schemes under different scenarios are optimized and scrutinized. The results show that out of the 8 billion m³ of first phase WRP diversion 3.37 billion m³ is allocated to in-stream ecological use and 4.63 billion m³ to off-stream socioeconomic use. More than 95% of the WRP diversion is allocated to the upper and middle reaches of YRB, and water shortage rate at the basin level is reduced to 7.0%—8.3%. The optimized allocation reflects the principle of ecological priority, ensures basic in-stream ecological water use, balances equity and efficiency of off-stream socioeconomic water use, and reduces water shortage effectively.