Water resources security in Hunan Province plays an important role in maintaining water security in the middle and lower reaches of the Yangtze River. The spatial evaluation and obstacle factor diagnosis of water resources security in Hunan Province are aimed to provide decision-making basis for regional ecological management and water resources development and utilization. Here, 13 indices from subsystems of water resources condition, social economic condition and ecological environment condition were selected to construct a spatial evaluation index system of water resources security, then the entropy weight-TOPSIS model was used to evaluate the comprehensive situation of water resources security, and the spatial distribution map was drawn. Meanwhile, the main obstacle factors were identified by obstacle degree model. The results show that the water resources security of Hunan Province was at level Ⅲ (basic safety) from 2000 to 2015, and reached level Ⅱ (relatively safe) by 2020, which showed an annual improving trend, keeping pace with the achievements of water conservancy constructions. In the research period, the spatial differentiation of water resources security was distinct, Chenzhou City maintained a high-level water resources security, whereas Xiangtan and Hengyang City were at a low level. The main obstacle factors of water resources security in Hunan Province were GDP, population density, water consumption per unit of farmland effective irrigation, water consumption per unit of industrial added value and water consumption per unit of GDP. The water resources security level of Hunan Province has been steadily improving in the research period, it is suggested that the further optimization of the unsafe areas should focus on the main obstacle factors.