In the transition zone between the Tibetan Plateau and the arid region of northwestern China, the spatiotemporal patterns and environmental controls of stable isotopes in precipitation remain unclear. A network of 19 sampling stations was established across the Qilian Mountains to observe stable isotopes in precipitation, and 1310 precipitation event-scale samples were collected. The local meteoric water line (LMWL) was obtained and expressed as 6D 7.996180- 1457 (R-2 0.96). The spatiotemporal patterns of the stable isotopes were mainly dominated by the co-influence of the water vapor sources and the local environment.The westerly circulation, monsoon circulation, and Arctic circulation accounted for 79%, 13%, and 8% of all precipitation events in the study region, respectively. The rainout process also caused oxygen isotope depletion for continuous precipitation events. When the temperature increased by 1 degrees C,6180 increased by 0.47%., but this increase varied with the temperature range. The effect of precipitation amount was apparent in summer and was caused by sub -cloud evaporation. In addition, 6180 decreased by 0.13%. for every 100 m increase in altitude in the Qilian Mountains. Future research should focus on quantifying the co-influence of sub-cloud evaporation, local moisture recycling, and water vapor sources on stable isotopes in precipitation. (C) 2020 Elsevier B.V. All rights reserved.