A novel strain sensor based on phase-shifted fiber Bragg grating (PSFBG) is designed. A PSFBG and a fiber Bragg grating (FBG) are connected together by an optical circulator, and symmetrically pasted on the uniform strength cantilever beam along the median. Both of them are the main sensing component of the strain probe. Because the location is next to the median, they have the same strain, and create sensing light which carries information and has extremely narrow line-width. Finally, the strain can be demodulated by an edge filter. The sensing light is got by theoretical simulation, and in experiment its line-width is only 101 pm. The experimental results are in good agreement with numerical simulation. In the experimental verification of strain sensor, the demodulation results have a good linear relationship with the signal to be measured. The fitting goodness is 0.994, and the resolution of strain probe is 1.5 με. The strain sensor based on this design is of high resolution and low cost, and is not chirped. It has a good practical value.