This paper concerns the theoretical analyzing about the information capacity and characteristics of the echo's polarimetric components, in through-the-wall scene, resorting to the polarimetric scatter matrix. The expressions of the four polarimetric components are proposed. Based on the reasoning, we deeply analyze the characteristics of each component and its effect on the imaging, detection and further process. Then some suggestions about optimal application of the polarimetric components are given. Experiment results validate this paper. What's more, the reasoning, in this paper, also applies to other signal format after simple transformation.