###### Abstract  
The interaction between soil moisture (SM) and evaporative fraction (EF), which reflects the degree of exchange of water and energy between the land and the atmosphere, is an important component of the theory of land-atmosphere coupling. Exploring the relationship between SM and EF in the transitional climate zone of China can help deepen our understanding of the characteristics of water and energy exchange in this region of strong land-atmosphere coupling. Data on observations in fluxes in the transitional climate zone revealed that fluxes in the energy on the surface of the land in this region exhibited significant inter-annual variations. The sensible heat flux (SH) exhibited the largest fluctuations in July and August, while the latent heat flux (LE) varied the most from June to August. The EF was found to exhibit weak correlations with indicators of vegetation growth such as the leaf area index, Normalized Difference Vegetation Index, and gross primary productivity in the transitional zone of the East Asian summer monsoon. By contrast, the relationship of land-atmosphere coupling between EF and SM in the transitional climate zone was stronger. Based on an analysis of the consistency of the relationship of SM-EF coupling, when the SMP reached 35%, there was a significant transition in the linear relationship between the SMP and EF that was consistent between the shallower and deeper layers of soil (0-40 and 40-80 cm). However, neither level had SM that reached saturation during the six-year observational period (2007-2012), and the mean values of its probability density function showed that the deep soil was drier than the shallow soil. This characteristic shows that SM plays a dominant role in variations in the EF in the transitional climate zone, which in turn indicates that constraints on the moisture govern the SM-EF relationship. The results of this study provide a better understanding of the mechanisms of land-atmosphere coupling in the transitional climate zone of China. climate transition zone; soil moisture; evaporative fraction; coupling relationship 202320202  
land-atmosphere interactions has become a crucial objective in the field of land-atmosphere coupling. Drawing on the conceptual model proposed by [PERSON] et al. [3] and incorporating the findings from [PERSON] et al. [4], [PERSON] et al. [5], and [PERSON] et al. [6], [PERSON] et al. [7] categorized the dominant factors controlling evapotranspiration into three types based on the quantitative relationship between evaporative fraction and soil moisture: A soil moisture-limited region, an energy-limited region, and a region with joint energy and soil moisture limitations. Large variations in the soil moisture (SM) and ET in zones of climate transition can lead to the transfer of moisture and energy to the upper atmosphere through the exchange of water vapor and energy. This results in a weakening of atmospheric stability and an increase in atmospheric disturbances, because of which zones of climate transition are regions featuring strong land-atmosphere coupling [8]. For example, the climate transition zones in the North American Great Plains, the Sahara region, Equatorial Africa, and Asia are all global hotspots for land-atmosphere coupling [4]. The strength of the coupling between ET and the atmosphere is three times that of the coupling between the SM and the atmosphere in the climate transition zone in the Great Plains of the southern United States [9], and this leads to frequent and severe weather events in the region. The climate transition zone in China is not only the region with the highest variations in ET but also serves as a semi-arid zone of transition in which the humid climate of the southeast transitions into the arid climate of the northwest [8]. It is also a zone of ecological transition from broadleaf forests to grasslands and deserts [10]. Previous research has shown that some weather-related and climatic phenomena in the zones of climate transition are significantly different from those in other climatic regions.