In order to better understand water use characteristics of Cinnamomum camphora, based on stable isotopes of stem water, leaf water and soil water of C. camphora during growing seasons (April-October) of 2017—2019 and corresponding environmental factors in the same period, as well as transpiration rate during the growing season of 2019—2021, we analyzed the relationship between plant water isotopes and influencing factors of C. camphor plants at daily scale, explored the variation characteristics of water absorption depth of C. camphor under different environmental conditions during the growing season. The results showed that in the sunny day, the δ¹⁸O of leaf water and transpiration rate were higher in daytime than those at night, while the δ¹⁸O value of stem water was lower in daytime than that at night. The time lag between transpiration rate and leaf water δ¹⁸O was larger on the sunny day in August than that in May, and the average time lag was 2.32 h. On the sunny day in May, the δ¹⁸O of leaf water and stem water had a quadratic function with temperature, vapor pressure difference, relative humidity and transpiration. On the sunny day in August, there was a quadratic relationship between leaf water δ¹⁸O and the above factors, but there was no obvious functional relationship between stem water δ¹⁸O and the above factors. The water absorption depth of C. camphora had obvious seasonal variation characteristics. At the beginning of the growing season (April-May), C. camphora had single water-absorbing layer, mainly used shallow soil water. It had two water-absorbing layers during the middle growing season (June-August) and the late growing season (September-October). C. camphora used middle and deep soil water in the middle of the growing season, while it used shallow and deep soil water in the late growing season. The water absorption depth and transpiration were also affected by habitat. During seasonal drought, the width of the diurnal variation curve of transpiration gradually narrowed with the duration of drought, and the water consumption of transpiration decreased correspondingly. Affected by environmental changes and its own physiological characteristics, water absorption depth of C. camphora gradually changed from shallow to deep and then shallow. However, compared with that before precipitation, transpiration of C. camphora increased after precipitation, the water absorption depth moved up, and the water absorption layer became narrow.