【Objective】In order to explore temporal variation of stable isotopes in soil water and distribution in soil profile, and to characterize the soil water line (SWL) in the monsoon region, this research project was launched, which was expected to be conducive to a better knowledge of redistribution processes of soil water. 【Method】 In this study, monitoring was carried out of stable isotopes in ground water in the soil profile (0-130 cm), precipitation and groundwater, and relevant environmental factors (including soil water content, soil temperature and meteorological variables), in a Cinnamomum camphora forest in Changsha from March 2017 to February 2019, and the monitoring data were collated and analyzed to determine variation of stable isotopes in soil water and rain water and its influencing factors. 【Result】 Stable isotopic composition of the soil water in the 0-60 cm soil layer varied significantly with the season, and the variation lagged by a varying degree behind that in rain water. The mean monthly maximum hydrogen stable isotope ratios (δ²H) in soil water regardless of soil depth all appeared all in May, and the mean monthly minimum one did in the period from September to December. However, no obvious seasonal variations were observed in the soil water and ground water below 60 cm in depth. All the above findings suggest that rain water may directly affect the soil water in the 0-60 cm soil layer and the soil water in the soil layers below and groundwater may preserve more data of stable isotopes in rain water accumulated from preceding rainfall events. Difference of the δ²H in soil water from the local meteoric water line (LMWL) increased in mean lc (Line-conditioned excess) with soil depth, decreased in standard deviation and gradually leveled off, which suggests that evaporation of soil water gradually decreases with soil depth. Significant and positive relationships were found between lc andδ²H in soil water at all soil depths. That is to say, the higher the δ²H in soil water, the lower the deviation degree of δ²H in soil water from the LMWL, and the weaker the evaporation of soil water; and likewise the lower the δ²H in soil water, the higher the deviation degree of δ²H in soil water from the LMWL, and the stronger the evaporation of soil water. Correlation analyses of lc in soil water at various soil depths with accumulated atmospheric evaporation (∑E) and accumulated atmospheric temperature (∑TA) in the preceding period shows that the latters significantly affected lc in soil water in the 0-60 cm soil layer, but insignificantly in soil layers below 60 cm in depth. Moreover, a certain relationship was found between soil water content (θ) and lc in soil water. The study also shows that relatively low stable isotope ratios in soil water in all soil layers were observed mostly during warm seasons relatively high in ∑E and ∑TA, and during the seasons evaporation enrichment grew stronger, while lc in soil water did lower, thus making scatter points of stable isotopes in soil water deviate further from LMWL; while relatively high stable isotope ratios in soil water in all soil layers appeared mostly during cold seasons, relatively low in ∑E and ∑TA, and relatively weak evaporation enrichment and relatively high lc in soil water during the seasons made scatter points of stable isotopes in soil water close to LMWL. Therefore, the slope of SWL was higher than that of LMWL in all soil layers in this study area. 【Conclusion】Stable isotopes contained in atmospheric precipitation are a direct factor affecting stable isotopes in soil water. Abundance of the stable isotopes in soil water is related to atmospheric heat and humidity in the preceding period. The cause why the slope of SWL is higher than that of LMWL in all soil layers is negatively and seasonally related to stable isotopes in precipitation and evaporation enrichment intensity of stable isotopes in soil water.