Abstract: Based on the precipitation observations from the China Meteorological Administration, the Japanese 55-year Reanalysis (JRA-3Q), and the Hadley Centre sea surface temperature dataset for 1980- 2024, this study investigates the long-term trend of June precipitation over Jiangxi Province using a moisture budget diagnosis and circulation analysis, and further verifies the large-scale circulation response with a linear baroclinic model (LBM).The results show a significant increasing trend in June precipitation over Jiangxi Province, with more pronounced increases in the southern and northeastern parts of the region. The moisture budget analysis indicates that the precipitation increase is primarily dominated by the dynamic component of vertical moisture advection, suggesting that enhanced upward motion plays a crucial role. The thermodynamic component of vertical moisture advection and the dynamic component of horizontal moisture advection also contribute positively, which are mainly associated with the strengthening of the low-level southwesterly monsoon flow and the increase in specific humidity. Further analyses reveal that the sea surface temperature over the Pacific exhibits a La Niña-like pattern with cooling in the eastern Pacific and warming in the western Pacific in recent decades. This pattern strengthens the tropical Walker circulation and enhances convective activity and diabatic heating over the Maritime Continent. The anomalous diabatic heating over the Maritime Continent excites an anomalous meridional circulation, leading to the formation of a low-level anomalous anticyclone over the South China Sea-western Pacific region. On the northern flank of this anticyclone, enhanced southwesterly winds increase low-level moisture convergence and upward motion over Jiangxi Province and transport more moisture from low latitudes, ultimately resulting in the long-term increase in June precipitation. The LBM simulations successfully reproduce the atmospheric circulation response to the tropical thermal forcing, supporting the robustness of the proposed physical mechanism.