[Background] The Loess Plateau, which is characterized by weak ecological environments and scarce water resources, is located in the Northwest of China. Due to the development of economy and increment of population, this region has been faced with the increasing pressure of water resources shortage. In order to achieve the scientific allocation and efficient utilization of water resources in watershed, it is of great significance to conduct the investigations on characteristics of waters transformation in the area. [Methods] As typical case for study, the Jiuyuangou Watershed, which is located in Suide County, Yulin City of Shaanxi Province, was selected to investigate the characteristics of waters transformation in the loess hilly and gully regions. Precipitation samples, gully-channel water samples and well water samples were collected and tested to quantify the compositions of the hydrogen and oxygen isotopes in each water during Sept. 15 to 19, 2014. [Results] By analyzing the relationships between δD and δ¹⁸ O in the gully-channel water and well water of Jiuyuangou, it was found that the evaporation line equation of gully-channel water was EL-1: δD = 5.40 δ¹⁸ O - 20.34(n = 13, R² = 0.99), and the evaporation line equation of the gully-channel water and well water was EL-2: δD = 5.33δ¹⁸O - 20.89(n = 19, R² = 0.98). Additionally, the temporal and spatial variations of δ¹⁸ O in gully-channel water and well water were illustrated in the paper. It was visualized that the δ¹⁸O in gully- channel water on Sept. 16 was the lowest during the period of sampling, and the δ¹⁸ O in gully-channel water increased progressively from the upper to the lower reaches of Jiuyuangou Watershed. The δ18 O of well water tended to be more positive and more stable than that of gully-channel water. The impacts of rainfall, air temperature and wind speed on the variation of δ¹⁸O in gully-channel water was greater than that on the variation of δ¹⁸O in well water. It was concluded that the surface water and ground water in Jiuyuangou Watershed were both supplied by atmospheric precipitation. The weighted average value of hydrogen and oxygen stable isotopes in precipitation which could effectively recharge the ground water was δ¹⁸O = -11‰and δD = -79.80‰respectively. Besides, the gully-channel water and well water in the upper reaches presented a similar evaporation trend with similar slope and intercept, implying that there was some degree of transformation between them. Furthermore, the main transformation relationship between the gully-channel water and well water was characterized by unidirectional recharge from the gully-channel water to the well water with a slow recharge rate, indicating that the retention time of the water in Jiuyuangou Watershed was longer. [Conclusions] Finally, based on the above results, water loss caused by evaporation in the transformation process between the gully-channel water and well water is also calculated using Rayleigh distillation model and regression equation between absolute temperature T and fractionation factor 18αw - v and 2αw - v with an assumption that the water vapor exchange is equilibrated. The estimated result shows that the gully-channel water will lose 7% during the transformation process.