The stable isotopic composition of rainwater (d(18)Op and dDp) has been considered an effective proxy in studying atmospheric circulation and hydrological cycle processes. However, the linkage between variabilities in moisture sources and d(18)Op remains poorly understood in Southwest China. Here, we utilized three long-term (10-year) d(18)Op records (Beibei, Furong, and Yangkou stations) in Chongqing, Southwest China, from 2010 to 2019 A.D., integrated with a cluster analysis based on the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) to quantitatively demonstrate the close remote coupling of moisture sources and d(18)Op on seasonal and interannual timescales. The clustering calculation results indicated that the percentage initial moisture source proportions of the westerlies and Asian summer monsoon have changed significantly at seasonal and interannual timescales, leading to the significant variation in d(18)Op in Southwest China. Domination of westerlies and inland moisture contribution resulted in the positive d(18)Op excursion in the dry season (November, December, January-April) while prevailing oceanic moisture led to the negative d(18)Op excursions in the rainy season (May-October). On the interannual scale, d(18)Op and d-excess exhibited a persistent positive/high trend, which is consistent with a decrease/increase in water vapor contributions from the ocean/westerly sources. Furthermore, d(18)Op showed a good correlation with the Indian Ocean Dipole index, El Nino-Southern Oscillation, and the South Asian monsoon index, indicating that large-scale circulation patterns may affect regional d(18)Op through their influence on moisture transport and convective activity in the source region. The long-term observation confirmed changes in moisture sources largely depend on the Westerly and Indian monsoon dy-namics controlled by ocean-atmosphere circulation, supporting the effects of moisture sources on the rainwater isotopic composition.Read less <