Abstract: Fog is one of the important parts of horizontal precipitation in forest ecosystem. Based on stable isotope technique with high sensitivity and quantification is the focus research of forest hydrology to analyze the role of fog water in the water cycle in forest ecosystem. The paper summarized the canopy interception fog, forests utilization of fog water and fog water recharge soil water and groundwater, provided a reference for the use of hydrogen and oxygen stable isotope technique to study the foggy mountain ecosystem and coastal ecosystem in the forest hydrological effects.