To investigate the impact of intensified seasonal drought under climate change on evapotranspiration in red soil farmland ecosystems in southern China and its driving mechanisms, this study was conducted on typical red soils derived from Quaternary red clay in Jiangxi Province using a large scale lysimeter. Four treatments were applied: control (CK), 25% rainfall interception (P-25%), warming by +2°C(T+2°C), and their combination (P-25%+T+2°C), to assess the effects of drought regimes on soil moisture dynamics in the 0–150 cm profile, evapotranspiration, and their driving factors. All drought treatments significantly reduced soil moisture content and water storage in the 0–150 cm profile by 2.5~15% and 2.52~14.67%. Among these, the shallow (0-40 cm) layers were most sensitive to rainfall variation, whereas the deeper layers (100 cm and 150 cm) remained relatively stable. During the wet season (January to June), the water content variation in the 0-40 cm soil layers was most significant under the treatments of P-25%, T+2°C and (P-25%+T+2°C) with reductions of 4.92%, 3.63% and 13.90%, respectively, compared to the control (CK). Meanwhile, the (P-25%+T+2℃) treatment showed the greatest variation in soil moisture content across all soil layers. In the dry season (July–December), similar patterns were observed but with greater decreases. Daily evapotranspiration ranged from 0 to 20 mm. Compared with CK, T+2°C increased evapotranspiration by 5.17%, whereas P-25% and P-25% + T+2°C reduced it by 16.42% and 14.17%, respectively. Evapotranspiration fluctuations were significantly smaller during the wet season than in the dry season. Structural equation modelling revealed that P-25% reduced the contributions of meteorological factors (moisture and heat) to evapotranspiration (by 13.2% and 17.2%, respectively), while enhancing the direct effect of soil moisture (55%). In contrast, T+2°C strengthened the dominant role of meteorological moisture (37.9%), but diminished the influence of meteorological heat and soil moisture (15.4% and 77.8%). The combinedP-25%+T+2°C treatment reduced the total effect of the heat factor by 24.2%. In summary, Warming and rainfall interception in red soil regions have reduced soil water deficits and intensify soil evaporation, thereby amplifying seasonal drought stress. These findings provide valuable theoretical and empirical evidence for improving agricultural water cycling and drought mitigation strategies in southern China’s red soil regions under future climate change scenarios.