Introduced is a method based on optical fiber sensing technology for measuring the natural frequency of uniform cantilever beam, and it was verified by theoretical calculation and software simulation. Firstly, the relationship between the central wavelength of the fiber grating and the deflection at the location of the cantilever was deduced. Secondly, according to the analysis of the relationship between the central wavelength of grating and the deflection of cantilever beam, an experimental measurement system was built, and an initial step signal of 20.093Hz was generated by firing the connected line in the experiment. Thirdly, the natural frequency of the beam was calculated as 20.311Hz by Ritz method. Finally, the modal analysis of the beam was carried out by using ANSYS software, and the result is 20.44Hz. The experimental result is very close to that of the theoretical calculation and the finite element simulation. It is proved that the experimental method is correct and feasible, providing a new, simple and feasible method for obtaining the natural frequency of the cantilever beam.