Refractive index sensing characteristics of a microstructured optical fiber Bragg grating(MOF-BG) based on dual-polarization mechanism are investigated.The finite element method is adopted for calculating the propagation characteristics of a polarization-maintaining MOF.And the single-mode transmission scope is analyzed.Furthermore,the coupled-mode theory is adopted for simulating the reflection spectra of the Bragg fiber grating in the MOF when injecting different media.The relationship between the center wavelength difference of two polarization modes and the refractive index of the medium is analyzed.Ultimately,the corresponding polynomial equation is fitted.Simultaneously,the temperature characteristic of the PM-MOF is also considered.The results demonstrate that the two polarization modes respond similarly to the temperature,and the method based on two polarization center wavelength difference possesses the anti-interference ability.The results provide the theoretical basis for the applications of the PM-MOF Bragg grating in the optical fiber biosensor.