Precipitation and evaporation are important parts of the hydrologic cycle. Raindrop is subjected to sub-cloud evaporation as it descends from the bottom of clouds to the ground. It was changed in the degree of sub-cloud evaporation and precipitation isotopes on the ground with seasonal changes in meteorological factors such as temperature and precipitation. Based on the precipitation isotopes and meteorological data at Zhangye station, this study analyzed the degree of sub-cloud evaporation and its relationship with hydrology (precipitation amount), meteorological (relative humidity, temperature) elements to reveal the influence of different meteorological factors on sub-cloud evaporation, on the base of clarifying the changes of atmospheric precipitation isotopes and the influencing factors. The results show that the precipitation stable isotopes at Zhangye station are mainly affected by temperature, and characterized by obvious seasonal changes with rich in summer and depleted in winter. The slope of the Local Meteoric Water Line is 7.02, which is lower than that of Global Meteoric Water Line, because the raindrops are affected by the sub-cloud evaporation with falling. Sub-cloud evaporation is most affected by relative humidity, followed by precipitation amount, and air temperature also has an effect on it.