The high impedance grounding fault in power distribution networks has weak electric capacity and complex fault characteristics, so the success rate of detecting such fault is low. If the fault occurs and cannot be found and removed in time, it may bring great harm to the safety of equipment and personnel. Existing research on different types of high impedance grounding medium, especially the human body medium, is insufficient to analyze the impedance property and fault characteristics. For this problem, based on the logarithmic arc model and human impedance model, the impedance characteristics of non-living body conductive medium and human body are compared and analyzed from time and frequency domain aspects using the techniques of graphic morphology analysis, Fourier transform and so on. Also, combined with the field test data, the impedance features and typical fault features of the two types of grounding media are verified. The above analysis lays a foundation for the subsequent design of an effective detection scheme for a high impedance grounding fault in power distribution networks. This work is supported by the National Natural Science Foundation of China (No. 52077116) and the Science and Technology Project of Guangdong Power Grid Co., Ltd. (No. GDKJXM20184472).