The coupling characteristics of dual-core photonic crystal fiber with rectangular holes array are researched based on horizontal coupling theory of parallel waveguide. The affections of fiber′s structural parameters for coupling characteristics are numerically calculated. The simulation results demonstrate that enlarging hole pitch in vertical or reducing hole pitch in horizontal and decreasing hole diameter can shorten the coupling length of fiber and the difference of coupling length in X- and Y- polarization. A kind of polarization splitters based on rectangular lattice structure with minimal coupling length (125 μm) and higher extinction ratio (38 dB) is designed.