Abstract: As poor geological conditions at the foundation of open diversion channel of Tongzilin hydropower project, thick overburden layer at the end of the channel made foundation excavation method ineffectual. Sash-shaped underground continuous wall was used to reinforce the soft foundation. Being foundation of major structure, it retained soil and water, bore vertical and horizontal load. However, it was rarely used as structure foundation in hydraulic projects. The paper introduced its structural characteristics and key construction points, for reference.