Aiming at the insufficient capacity for the general optical fiber fluorescence sensors to collect the fluorescence, a novel fluorescence sensor filled with high index solution was designed that doped dyes in the air holes of microstructured optical fiber. Using the adjustable boundary condition fourier decomposition method, the mode field distribution of this microstructured fiber was given, and the fluorescence capture fraction was calculated under the influences of optical fiber structural parameters and the refractive index of solution. The results show that small core radius and higher refractive index of solution than that of core materials can enhance the absorption of the excitation light, and increase the fluorescence capture fraction and the sensitivity of these fluorescence sensors.