Based on the summer precipitation, river water, soil water and spring water δ2H and δ18O data in the Buha River Basin, this paper analyzed the characteristics of stable isotopes and d-excess in different water bodies in the study area, discussed the influence of altitude on the stable isotopes of river water and soil water, and simulated the source of precipitation water vapor by using the backward trajectory model. The results showed that: (1) The stable isotope values of water from large to small were as follows: soil water> river water> spring water > precipitation, and the stable isotope variation range of precipitation was greater than that of river water, soil water and spring water, and the mean value of d-excess of precipitation was the largest, and the mean value of d-excess of soil water was the smallest. (2) The atmospheric precipitation line in the Buha River Basin in summer is δ2H=8.34δ18O+36.05 (R2=0.99), and its slope and intercept are higher than those of river water, soil water and spring water. (3) The river water δ2H and δ18O were spatially low in the northwest and high in the southeast, which were negatively correlated with altitude. Soil water δ2H and δ18O were high in the northwest and low in the southeast, which were positively correlated with altitude, and the elevation effects of river water and soil water were not significant. (4) The backward trajectory simulates that the summer precipitation water vapor in the Buha River Basin mainly comes from the Atlantic water vapor carried by westerly winds, accounting for 50%, and the low-altitude water vapor source is dominated by locally evaporating land air masses. The results of this study can provide a theoretical basis for the hydrological cycle and climate response in the Buha River Basin.