The relationship between UV photo-induce index changes of single mode hydrogen loading fiber and its dose is studied experimentally. Maximum reflectivity model and reflectivity notch bandwidth model of uniform grating are proposed respectively for different fiber grating strength caused by its dose and the influence on AC result of Bragg reflectivity wavelength deviation are analyzed relatively. Results based on experiment and measurement data indicate that, when 244 nm argon ion laser emits 40 mW UV light, the curve of refractive index changes in single mode hydrogen loading fiber is exponential type (Ac=1.632×10-6 t 0.76912), exponential growth is obvious in the beginning, a very good linear region is following, and then refractive index increments reach saturated.