With the development of remote sensing technology, it is important to study on the thermal infrared polarization characteristics of the land surface objects. In order to explore the thermal infrared polarization characteristics of the grassland withered plants, the samples of the grassland withered plants were measured indoor according to the thermal infrared polarized detection mechanism, using thermal infrared radiometer. The results showed that the thermal infrared polarized radiance and brightness temperature have increased with the viewing angle and have increased first and then decreased with the azimuth and polarized state. Chloris virgata’s brightness temperature decreased first and then increased at 180° azimuth, which is an exceptional case. These reflect that the thermal infrared polarization characteristics are related to the materials’ roughness, the detecting direction, the internal structure and its emission ability, and this research laid the foundation for other quantitative studies.