The U.S.Mexico water debt is an international water rights dispute between the United States and Mexico over the development and utilization of the Rio Grande River since the 1990s. The climate of the Rio Grande River basin, the conception of water sovereignty and the institutional arrangements of both sides in solving the international river water resources determine the longterm and complexity of the U.S.Mexico water debt issue. In the future, the two countries will not overthrow the original international treaties and will not conclude new agreements, but will still coordinate the water debt issue within the framework of the basic framework formed by the 1906 and 1944 water treaties. In addition, the farmers’ conflict at the U.S.Mexico border, the newlybuilt boundary border wall, water delivery time, water ecological environment protection, and the border groundwater decrease caused by the AAC canal will all have significant impacts on the U.S.Mexico water debt. The new development of international water rights of the two countries can provide certain lessons for China’s relevant water policies.