Abstract: In order to improve detection performance of hidden human targets in foliage environment, this paper utilizes a ground-based ultrawideband (UWB) radar to study the effects of polarization and humidity conditions on the statistical characteristics of foliage clutter. For two common foliage clutter environments, the stepped frequency continuous wave (SFCW) UWB radar with the ultra-high frequency (UHF) band is used to measure multiple groups of echo data under horizontal and vertical polarization, dry and wet conditions, respectively. Radar echo signals are preprocessed. The amplitude values of multi-channels are calibrated before the histograms of the actual clutter amplitude are drawn. Five statistical models are used to fit the statistical distribution characteristics of the foliage clutter. The root mean square error (RMSE) between the fitting distribution and the actual distribution is implemented to quantitatively evaluate the fitting precision of the model. The analysis results show that polarization will not change the optimal fitting Weibull distribution of shrub clutter, but only the shape parameter range. When polarization changes from horizontal to vertical, the shape parameter range changes from 1.6477–1.8655 to 1.8396–1.910 7. However, for the arbor clutter, when polarization changes from horizontal to vertical, the optimal fitting distribution changes from Log-logistic distribution to Weibull distribution. The humidity condition does not change the optimal fitting distribution type of foliage clutter. The higher the humidity, the larger the shape parameters of the optimal fitting distribution, the wider the histogram and the longer the tail. The optimal distribution models and the range of related estimation parameters of two typical foliage clutter under different polarization and humidity conditions are drawn from this study, which has guiding significance for the research of foliage clutter modeling and target detection in foliage environment.