Abstract: With regard to the technical and theoretical problems of development and engineering safety guarantee of landslide-dammed lakes, the deformation and stress monitoring technology of concrete cut-off wall of dammed body and its installation method based on the distributed optical fiber sensing technology are designed and proposed. It has been successfully implemented and applied to the safety monitoring of the concrete cut-off wall of Hongshiyan dammed body. The deformation and stress regulations of the concrete cut-off wall of the Hongshiyan dammed body at the initial stage of water storage are analyzed and discussed. At the initial stage of water storage, the wall concrete is subjected to pressure in general and obviously affected by the impoundment process. There is more stress concentration in the supporting force of rockfill to the cut-off wall, and the materials of dammed body are obviously inhomogeneous. At the initial stage of water storage, the stress of concrete wall is far less than the strength index of concrete materials. The cut-off wall has good safety margin, and can effectively ensure its long-term deformation and stresssafety.