Based on the introduction of sensing principles of short-period fiber Bragg grating (FBG) and micro-nano fiber Bragg grating (MNFBG) refractive index and how to improve FBG refractive index sensing sensitivity, the research progress of two refractive index sensing technology schemes such as etching and polishing methods are described in detail. The advantages and disadvantages of the two schemes are compared and analyzed. The research status of micro-nano fiber and fiber grating used in refractive index sensing is summarized. The technology problems and solution schemes on current research are proposed and the development trend of FBG refractive index sensing technology is forecasted, which provide a reference for further research on refractive index sensing based on fiber grating devices.