Ecological water demand is an important aspect for the research of water supply-demand balance, which has a significant impact on regional ecological security and sustainable development. Although many ecological water demand models have been explored, a unified and complete regional ecological water demand model (REWD) has not yet been formed due to insufficient understanding of the connotation and composition of ecological water demand. Therefore, we redefine and clarify the composition of regional ecological water demand from the perspective of ecosystem division, and divide regional ecological water demand into biological water demand (BWD) and abiotic water demand (AWD). On this basis, a comprehensive regional ecological water demand model was constructed, which includes two major parts: the biological water demand model and the abiotic water demand model. The article applied the model to calculate and evaluate the ecological water demand in the Hanjiang River Basin (HRB), and estimated the ecological water-satisfied degree in the study area. The results show that, the range of ecological water demand in the study area is 481-2567,373 m3 /a, with the largest ecological water demand in the rivers and relatively small ecological water demand in the north-western region. The ecological water-satisfied degree in the HRB is basically above 100 percent, which is higher in the northeastern and southern parts of the basin, and lower in the central and north-western areas. The integrated regional ecological water demand model is a unified and universal ecological water demand model, and the results can describe the spatial pattern of ecological water demand in a region and provide services for finer water resource regulation and allocation.