Cantilever plates are common structures, which have been widely utilized in engineering practice, including aerospace, rail transportation, civil engineering and other fields. The deformation estimation is always one of the important research contents. This paper aims to solve the problem of bending of rectangular elastic cantilever plates and proposes a method to solve it by establishing the relationship between strain and deformation. The finite difference expression of structural transverse deformation is achieved under the framework of linearly elastic small deflection theory. The distributed optical fiber sensor with the ability of high-density strain measuring is used to obtain the strain input required for the expression, and a method of error correction for deformation measurement is proposed. The technical feasibility and measurement accuracy of structural deformation estimation based on distributed optical fiber sensing technology are evaluated. Some dial indicators are used in the metal cantilever bending tests. Experimental results show that the maximum deviation between results from the estimation and the dial indicators is 2. 0 mm, which accounts 9. 22% of the indication from dial indicators. The distributed optical fiber sensing technology is competent to perform deformation estimation, which has the potential application prospect.