Abstract: The inner deformation monitoring of concrete face rockfill dams (CFRDs) is an important way to evaluate their deformation stability and safety. Aiming to overcome the limitations of the traditional monitoring technology in the inner deformation monitoring of high CFRDs, an inner deformation monitoring method based on the distributed optical fiber sensing technology is proposed. Through the application researches on a 200 m-level CFRD, the feasibility of the three optical fiber layout methods (respectively installed in the 45a I-beam, 6-point galvanized steel pipe and protective sand layer) for the horizontal displacement measurement is compared. The results show that the average maximum difference of the measured results of the three optical fiber layout methods is less than 1.0 mm, which verifies the feasibility and consistency of the three optical fiber layout methods. In addition, the calculated results of the three-dimensional FEM analysis and the measured results of the traditional water pipe settler are compared with those by the proposed method. It is shown that the results based on the distributed sensing optical fiber technology are almost consistent with the numerical ones, and the average error between the settlement results and the measured values of the pipe-type settler is less than 10 mm, indicating that the distributed sensing optical fiber technology can meet the inner deformation monitoring requirements of high CFRDs. The rationality and feasibility of the proposed method are verified.