Abstract: The scientific and reasonable deformation monitoring of rock and soil masses is an important index for the evaluation of stability and safety of geotechnical engineering. Given full play to the characteristics of distributed optical fiber sensing measurement technology, based on the specially designed optical fiber deformation test devices, a two-dimensional deformation monitoring method based on the distributed optical fiber sensing technology is proposed. The indoor two-dimensional deformation tests of sensing optical fiber under five kinds of horizontal displacement and settlement adjustment conditions and two sets of simulation and verification of the measured internal deformation of rockfill dam project are carried out. The research results show that the absolute errors of horizontal displacement and settlement measured by 40 groups of tests are less than 1 mm under the five kinds of test conditions. The two-dimensional deformation monitoring method has excellent performance. Based on the measured horizontal displacement and settlement data of a 200 m-high rockfill dam, the indoor simulation tests are carried out. The test results are in good agreement with the measured ones in terms of the curve form and measuring value. The 406 m-long measuring section is subjected to quasi-distributed monitoring with the spacing of measuring points of 3.3 m. The settlement measurement error of the measuring points is cm-level, and the horizontal displacement measurement error is mm-level. It is shown that the two-dimensional deformation monitoring method based on the distributed optical fiber sensing technology can meet the needs of deformation monitoring of rock and soil and has good application prospects.