<p>Determining the suitable surface area of terminal lakes in arid regions is crucial for both basin ecological security and efficient water use. Previous studies on lake area have primarily focused on establishing the minimum threshold, with limited research addressing the definition of a suitable area. In this regard, we developed an ecological security assessment system to determine the minimum suitable lake area threshold, and propose a maximum suitable lake surface area based on the maximization of ecological water use efficiency. From 1990 to 2020, the surface area of Ebinur Lake showed an increasing trend, ranging from 427.9 km² to 884.9 km², with the maximum occurring in April and the minimum in September. According to the ecological security assessment, the minimum suitable lake surface area for Ebinur Lake was found to be 497.8 km², which is 69.9 km² larger than the historical minimum lake level observed during the study period. From an ecological water efficiency perspective, the maximum threshold for a suitable lake surface was determined to be 609.9 km², which is 275 km² smaller than the historical maximum lake surface area during the study period. The satisfaction level of Ebinur Lake’s suitable surface area was found to be only 38.71%. To address this, we propose an ecological water supply model that leverages the reuse of irrigation and drainage water resources to mitigate water scarcity in terminal lakes within arid regions. This study provides important insights for the optimal allocation and scientific management of water resources in terminal lakes in arid areas.</p>