A new type single-mode single-polarization photonic crystal fiber based on index-matching coupling has been put forward and its principle has been elaborated. A full vector finite element method is employed to simulate the fiber properties. When polarization dependant loss is larger than 4.08 dB/m in the wavelength from 1.26 to 1.7 μm and as diameters of air hole 1 and 2 between central and edge cores are 2.4 μm, the bandwidth of single-mode single polarization can reach 440 nm. The x-polarized mode exhibits a high leakage loss of 26.93 dB/m and the y-polarized mode exhibits a low leakage loss of 0.01 dB/m at a wavelength of 1.31 μm; the x-polarized mode exhibits a high leakage loss of 38.66 dB/m and the y-polarized mode exhibits a low leakage loss of 0.05 dB/m at a wavelength of 1.55 μm as diameters of air hole 1 and 2 are 2.6 μm. This photonic crystal fiber has a high bandwidth and polarization dependant loss in the 1.31 μm and 1.55 μm communication window.