Abstract: This study aims to investigate the impact of polarization mode, distance, clutter environment, and human posture on target detection performance through the analysis of empirical data. A ground-based foliage penetration (FOPEN) ultra-wideband (UWB) fully polarimetric radar system is set up to to measure the polarization scattering intensity and signal-to-clutter-plus-noise ratio (SCNR) of a metal sphere and human targets with varying postures concealed in woods. The study analyzes the influence of factors such as polarization, distance, environment, and posture on target detection performance, as well as the alterations in the target polarization scattering matrix (PSM) due to the forest environment. The experimental results indicate that, in most cases, horizontal-horizontal (HH) polarization exhibits the optimal scattering intensity and SCNR for foliage penetration. Standing human targets are the easiest to detect, followed by sitting and lying postures. As the detection distance increases, the scattering intensity and SCNR of all polarization channels generally decrease. For targets obscured by tree trunks, the SCNR of cross-polarization significantly improves. The forest-penetrating medium environment causes changes in the target PSMs, and the underlying pattern is influenced by the type of penetrating medium, the nature of the targets, and their posture. This research lays the experimental foundation for enhancing the performance of ground-based UWB radar in detecting targets concealed in woods.