Abstract: By continuously observing the grounding resistance of three types of grounding devices and analyzing the influence of precipitation and temperature on grounding resistance, we find that grounding resistance has obvious seasonal variation. Both precipitation and temperature increase during the rainy season(April to September), and thus the ground resistance shows a downward trend. After September, as precipitation decreases and temperature drops, ground resistance gradually increases. This process continues until February of the following year. The change rate of ground resistance is closely related to the type and size of grounding device. The influence of precipitation on ground resistance is small when the precipitation is less than 20 mm. When the precipitation is too high and the soil moisture content is at a high level, excess precipitation will not cause a significant drop in grounding resistance. During this period, temperature plays a key role in the decline of grounding resistance. During a prolonged drought, the soil moisture content is low. The precipitation in this period will cause a significant drop in grounding resistance, while the effect of temperature is relatively insignificant.