A novel photonic crystal fiber refractive index sensor with a large dynamic detection range is proposed. Two air holes are used as analyte channels. One coated with gold layer is used as surface plasmon resonance to measure the liquid index below that of the quartz substrate and the other filled with the test liquid is used as the directional resonance coupling to measure the index that of above the quartz substrate. A broad index range of analyte from 1.33 to 1.52 with high sensitivity can be achieved. The properties of the index sensor are analyzed by finite element method (FEM) with the boundary condition of anisotropic perfectly matched layer (PML). The results show that the maximal sensitivities reach 13500 nm/RIU and 28700 nm/RIU when refractive index is in the range of 1.32 to 1.44 and 1.46 to 1.52 respectively, where RIU is refractive index unit.