A novel polarization splitter based on octagonal dual-core photonic crystal fiber (O-D-PCF) is proposed. The impacts of several fiber parameters on the coupling characteristics of the polarization splitter are investigated by full-vectorial finite element method (FV-FEM) in detail. Through optimizing the fiber configuration, a 4.267-mm-long polarization splitter with a bandwidth of 37 nm is achieved, and its extinction ratio (ER) is as high as 81.2 dB at the wavelength of 1.55 μm. Compared with the hexagonal dual-core photonic crystal fiber (H-D-PCF) based polarization splitter, both ER and bandwidth of the O-D-PCF based one are effectively improved.