Researches conducted by Changjiang/Yangtze River Scientific Research Institute on expansive soil in the middle route of South-to-North Water Diversion Project are reviewed, and the main achievements on the theory and test technology in this regard are summarized. In particular, research works related to the failure mechanism and treatment technology of canal in expansive soil regions supported by National Key Technology R&D Program are presented in details, and the latest achievements on expansive soil inclusive of the failure mechanism, rapid identification, shear strength tests, and treatment measures of expansive soil canal slope are introduced.