Abstract: The original anti-seepage curtain on the left bank riverbed of the Wudongde Hydropower Station was designed to pass through the upstream side of the factory buildings, and to turn upstream to the relative waterproof layer of Pt2-12y. For this layout, the anti-seepage effect is reliable, but the anti-seepage line is long, and further the upper connection section passes through the dissoluble limestone stratum, so grouting construction is more difficult. According to the geological conditions exposed during the excavation and the special supplementary exploration results, the studies on the anti-seepage backing layer, the three-dimensional seepage calculation and the structural stability and safety review were carried out. Based on the analysis results, the arrangement of the anti-seepage curtain on the left bank was adjusted to the Pt2-12l weak permeable layer, so the curtain length was reduced to 329 m. The research results can be a good reference for the selection of anti-seepage backing layer and the optimization of curtain layout in similar projects.