Abstract: Abstract: Evaporative fraction (EF) is an important parameter to estimate evapotranspiration (ET) for regional ecosystem, and also an indicator to evaluate the moisture status of the terrestrial ecosystem. Based on the climate data in China and moderate-resolution imaging spectroradiometer (MODIS) products such as MOD11B3, MOD13A3 and MOD12, this manuscript focused on the monthly mean EF estimation using the Priestley-Taylor model and EF validation using the ground-based eddy measurement data, analyzed the spatio-temporal patterns of monthly mean EF and evaluated its responses to the climate factors in the vegetated region in China, in order to obtain the seasonal change characteristics of EF and its sensitivity to climate. Results showed that monthly mean EF dynamics in the vegetation ecosystems had significant seasonal change characteristics. During the whole year, vegetation ecosystem in South China had a higher value than those in other regions in China. In spring, monthly mean EF increased in the south of Yangtze River and Sichuan Basin. And then the regions with high EF value expanded to the North China Plain and the Northeast China in summer. In autumn, the regions with high EF value shrank, and the distribution of monthly mean EF was similar to that in spring. The correlations between the spatial distribution of EF and climate factors showed seasonal variability. In spring and autumn, the EF was significantly correlated(P<0.01) with monthly total solar radiation, monthly mean temperature and monthly precipitation. In winter, monthly mean temperature was the sole factor significantly affecting(P<0.01) the EF in vegetation ecosystem in China. Contrary to these, there were no significant correlations between EF and climate factors in summer. The reason was the distinguishing relationships between monthly mean EF and climatic factors. Regional variability was also found in the sensitivity of seasonal EF to the climate. The higher sensitivity to monthly precipitation was found in the northern and inland regions compared to that in the southern and coastal regions. On the contrary, vegetation ecosystem in the southern and coastal regions showed higher sensitivity to monthly mean temperature and monthly solar radiation. This was accordant with the differences of the moisture conditions between northern and southern ecosystems. In Southwest China, the negative relationship between monthly mean EF and monthly mean temperature showed the drought in the hot season was controlled by the southwest monsoon in this region. On the Qinghai-Tibet Plateau, the sensitivity of monthly mean EF to climate was lower than that in other regions. Monthly mean EF of deciduous broadleaf forest, shrub land and grassland had high seasonal variability, while the seasonal variability on monthly mean EF of evergreen broadleaf forest was relatively insignificant. The relationships between EF and climatic factors for each vegetation type showed that monthly mean EF of cropland was more highly related to monthly precipitation, monthly mean temperature and monthly solar radiation than those of other vegetation types. Compared to cropland, monthly mean EF of forest showed less sensitivity to monthly precipitation. Among various forest types, monthly mean EF of mixed forest and evergreen broadleaf forest had the highest sensitivity to monthly solar radiation, followed by deciduous broadleaf forest, deciduous conifer forest and evergreen conifer forest, suggesting that the broadleaf forest had higher sensitivity to monthly solar radiation. Similar to the sensitivity to monthly solar radiation, monthly mean EF of broadleaf forest had a higher sensitivity to monthly mean temperature than that of conifer forest.