The power-referenced refractometer based on tilted fiber Bragg grating is investigated theoretically by complex mode coupled mode theory. The use of perfectly matched layer (PML) technique simplifies the radiation mode model. The numerical results show that with the increase of tilted angle,the sensing range shifts to smaller refractive index region. With the increase of the grating length and the index modulation strength,the sensitivity of the refractometer increases,but sensing range unchanged. This refractometer is polarization dependent,and the polarization dependency raise with the increase of grating tilted angle. Therefore,precise and stable polarization control is essential for such kind of sensing system.