A compact silicon-based polarization demultiplexer (P-DEMUX) is proposed by using a microring resonator, where the metal-loaded strip waveguides are used as the bus channels. The modal characteristics of transverse electric (TE) modes for the hybrid plasmonic waveguides are analogous to those for the strip dielectric ones, while those of transverse magnetic (TM) modes show significant differences, leading to strong polarization-dependence. Consequently, the input TE mode can efficiently output from the drop port at the resonant wavelength, while the input TM mode directly outputs from the through port with nearly negligible coupling. The present P-DEMUX can be easily employed to construct an on-chip wavelength/polarization division multiplexing optical transmission system, further increasing the optical interconnect capacity. Results show that a P-DEMUX with a radius of 2.003 μm for the microring is achieved at the wavelength of 1550 nm, where the extinction ratio and insertion loss are, respectively, ∼22.36 (20.09) dB and ∼0.39 (0.84) dB for the TE (TM) mode. In addition, fabrication tolerances to the key structural parameters are investigated and field evolution through the P-DEMUX is also presented.