<p>Soil moisture (SM) exerts a considerable influence on land-atmosphere coupling, particularly affecting the change of surface water availability (precipitation minus evapotranspiration, P–E) on global or typical hotspots. However, under global warming, the divergent response of P-E to SM in different climate regions and the underlying heterogeneity of SM-P-E coupling remain unresolved. Here our findings reveal that the response of P-E to SM is more pronounced in humid regions relative to drylands across both the history and future periods. For the historical period, based on three reanalysis datasets, analyzing from multiple perspectives, including climatology, trends in key factors of the water cycle and variability in land-atmosphere coupling index (LCI), we prove that P-E is more sensitive to SM in humid regions, being about 2.5 times greater than that in drylands. Under future climate scenarios, through CMIP6 model projections (SSP245 and SSP585 scenarios), comparing the difference in LCI between 1980 and 2014 and 2066–2100, we discover that the response of P-E to SM is mainly enhanced globally, especially in humid regions under the warmer SSP585 scenario. This enhancement is further supported by evidence from land-atmosphere coupling experiments. In drylands, the SM effect mitigates the drying effect by increasing ∆(P-E), which promotes the transition to wetting. In contrast, in humid regions, the SM effect amplifies the drying effect by decreasing ∆(P-E), which in turn suppresses the wetting trend.</p>