Abstract: To evaluate impact of rural black and odorous water governance engineering on irrigation water quality of surrounding farmlands, a typical rural black and odorous water governance engineering in Yongjing County, Linxia Hui Autonomous Prefecture, Gansu Provincewas selected as research object．A combination of systematic monitoring and comprehensive evaluation was adopted to track and monitor irrigation water quality before and after governance for three years across different seasons．Monitoring indicators included 12 routine water quality parameters such as pH value, dissolved oxygen（DO）content, chemical oxygen demand（COD）, ammonia nitrogen（NH₃-N）content, total phosphorus（TP）content, total nitrogen（TN）content, and heavy metals content．Results has showed that after comprehensive governance, pH value of irrigation water stabilized（6.9 to 7.3）, DO content increased significantly（by 78.3%）, COD decreased by 64.5%, NH₃-N content reduced by 81.2%, TP and TN content were reduced by 69.7% and 72.4%, respectively．All heavy metal contents met farmland irrigation water quality standards．Comprehensive pollution index decreased from 2.87 before governance to 0.52, and water quality grade improved from below Class V to Class III, with irrigation water quality meeting requirements of GB 5084—2021 Water Quality Standards for Agricultural Irrigation．Seasonal viriations in irrigation water quality were observed, with relatively poor water quality in summer, necessitating strengthened management．Research has demonstrated that rural black and odorous water governance engineering effectively improve irrigation water quality of surrounding farmlands, providing scientific basis for agricultural production safety and rural water environment improvement．