Abstract: The understory ground cover is treated as the second layer of forest hydrological process, which plays a very significant role in forest hydrological cycle and flood control and disaster reduction of river basins. On the basis of searching, reading, summarizing and summarizing the previous research results, this study clarified the hydrological process of forest floor, analyzed the action mechanism of biological factors, environmental factors and climate factors in the forest ground cover, and summarized its functions of water storage, soil conservation and water purification. The reserve of understory ground cover was directly proportional to its water holding capacity, and the water holding capacity of understory ground cover increased with the restoration of vegetation. The results of short-term water-holding capacity of ground cover results could not fully reflect the water-holding capacity characteristics of ground cover, and forest cover layer of hydrological process mechanism was still unclear. Therefore, it was necessary to strengthen the research from the following aspects in the future: (1) On the basis of long-term monitoring, modern science and technology such as remote sensing, isotope were used to realize large-scale nondestructive dynamic monitoring. (2) On this basis, multiple factors such as rainfall, rainfall intensity, rainfall duration, wind speed, temperature and humidity were considered to be included into the list of influencing factors to analyze their influence on the interception and delay function of the ground cover. (3) When studying the hydrological benefits of ground cover, water holding capacity, pore structure and enzyme activity of soil layer, as well as the species, quantity and activity of microorganisms should be included in the research system to systematically study the relationship between ground cover and soil physical and chemical properties. (4) Strengthen the analysis of water quality at different levels, and clarify the element absorption characteristics of the ground cover, so as to scientifically evaluate the health status of forest ecosystem