In order to clarify the correlation of a climate change and a forest surface change of state, data analysis was conducted concerning the secular fluctuation tendency of temperature and rainfall runoff and SS. And the model applicable in a forest basin was built and the microscopic soil particle quantity of production from forest ground was predicted based on the global warming scenario.<BR>Due to a pronounced increase in the number of days exceeding 25°C in the forest region, the quantity of soil moisture evaporation is increasing. As a result, the amount of soil moisture in the forest ground surface layer is decreasing. As soil moisture in the forest soil surface decreases, the soil's ability to resist the collapse of its aggregated structure decreases. Consequently, even small and medium-scale precipitation events can easily cause soil dissolving. When microscopic soil particles dissolve in large quantities, soil porosity increases, and the decrease in soil moisture and increase in subsurface flow rate combine to accelerate dissolving of microscopic soil particles, thus creating a vicious circle. Finally, changes in forest soil due to global warming can have a marked effect on forest ecosystems.