In order to reveal the hydrological process of the forest canopy and provide a reference for the scientific management of forest hydrological ecosystem, precipitation, throughfall, and canopy information were collected from typical Cinnamomum Camphora woods during April 2018 to March 2019 in Changsha to study the spatial variability of throughfall and the characteristic of stable isotopes in throughfall. The results showed that the total throughfall under the canopy was 340.1 mm, accounting for 71.2% of the total precipitation outside the forest; comprehensively affected by the canopy structure including the distance from tree trunk and the leaf area index. The throughfall presented great spatial variability and stable temporal variability.The correlation analysis showed that the coefficient of spatial variability decreased with the increase of precipitation, reflecting the important influence of precipitation characteristics on the spatial variation of throughfall.Compared with the amount of throughfall, the stable isotopic compositions in throughfall were hardly affected by canopy structure and atmospheric conditions,not obvious in spatial variation, and not stable in temporal variation. In most precipitation events,stable isotopes in throughfall were richer than those in precipitation, and there was no significant discrepancy between the mean values of them, indicating that throughfall underwent weak evaporation in its formation process. The deviation between the stable isotopes and d in throughfall and those in precipitation suggested that the canopy had the selective penetrating effect.