A polarization beam splitter based on a two-dimensional photonic crystal slab is presented. In the designed photonic crystal, the TE polarization is negatively refracted, while the TM polarization is positively refracted. The photonic crystal is composed of silicon pillars in a triangular lattice. The whole device is very compact (20×20μm2), and is compatible with the planar integration. The measurement results show that the extinction ratio is ~15dB from 1530 to 1610 nm.