WUE sensitivity to drought varies with the magnitude of the drought, the duration of the drought, and the type of biological community [18; 22; 23; 24]. Some researchers investigated the impact of drought events on the WUE of distinct vegetation types and found that the WUE of diverse vegetation types responded differently to drought [23]. A study of the responses of ecosystem WUE to meteorological drought (when dry weather patterns dominate a region) in northern China found that forests had the greatest tolerance to drought, followed by cropland, grassland, and desert, in that order [24]. There is still a lack of scientific consensus on the response mechanism of WUE to drought. Some studies have found that drought reduces WUE [25; 26], whereas others found that the response to drought includes increased WUE [27; 28; 29]. In addition, it has been found that WUE is also affected by the magnitude and seasonal nature of the drought. For example, [PERSON] et al. [30] found that drought increased ecosystem WUE in spring. [PERSON] et al. [19] found that drought decreased WUE in the summer but increased it in the fall, whereas there was no significant impact in the spring. [PERSON] et al. [31] found that extreme drought decreased ecosystem WUE in the spring and summer but increased WUE in the fall. This shows that WUE's response to drought requires more in-depth research. Although many scholars have studied the influence of drought on WUE and have drawn many valuable conclusions, most studies on the WUE sensitivity of different ecosystems to drought have been based on long-term drought; few research groups have paid attention to the impact of seasonal drought on the WUE of different climate regions, a relationship that is essential to understanding ecosystem processes under drought stress [8]. Moreover, there have been few studies on the impact of seasonal drought magnitude on WUE. The Loess Plateau in China is characterized by ecological fragility and climatic sensitivity. This region suffers from serious soil erosion, low vegetation coverage, and a continuous drought trend in recent years [32]. Furthermore, the WUE of the Loess Plateau is gradually decreasing, and the drought is becoming more and more serious, which has seriously threatened regional ecological security. However, studies on the response of WUE to seasonal drought is still lacking in the Loess Plateau in northwestern China. Therefore, the focus of this study is on (1) exploring the temporal and spatial differentiation character istics of seasonal drought and WUE in the Loess Plateau from 2001 to 2019; (2) analyzing WUE sensitivity to seasonal characteristic drought in the Loess Plateau; and (3) evaluating the impact of seasonal drought on WUE in different climate regions. The goal of this study is to provide as much understanding as possible of the response of terrestrial ecosystems to drought stress, with reference for the Loess Plateau, in order to carry out appropriate ecosystem management [5; 32]. Therefore, understanding the relationship between ecosystem WUE and droughs is necessary for evaluation of the ecological security of the Loess Plateau and has great practical significance and scientific value.