A polarization splitter based on metal-decorated microstructure fiber was proposed. The relationship between splitter length and structure parameters was analyzed by using full vectorial finite element method. The variation rules of splitter length with hole pitch and duty ratio for the polarization splitter were obtained. Numerical results shows that the length of the polarization splitter decreases with the decrease of hole pitch and the ratio of hole diameter to hole pitch. Considering both the properties and the transmission loss caused by metal, a simple-structure polarization splitter based on metal-decorated microstructure fiber was optimized. The length of the polarization splitter is as short as 3.523 mm and the extinction ratio reaches up to 74.9 dB at the wavelength of 1.55 μm. The bandwidth is 40 nm from 1.53 μm to 1.57 μm where the extinction ratios are more than 20 dB covering the C band of optical communication. At the same time, when the length of polarization splitter exists ±5% error, it can also keep good performance.