A Pressure-State-Response (PSR) model was developed to diagnose the sub-regional health of the Lake Wuliangsuhai in the Inner Mongolia.A total of 25 indicators including ecological character indicators,ecological function indicators and social environment indicators were combined to assess the ecosystem health of the lake.Expert Evaluation Method (EEM) and Analytic Hierarchy Process (AHP) were used to identify the weight of each indicator.The Lake Wuliangsuhai was classified into three sub-regions (Ⅰ,Ⅱ and Ⅲ) in consideration of their ecological and environmental characteristics.Results indicate that the lake is staying in a state of alarming or worse quality.The Comprehensive Health Indices (CHI) of three sub-regions are 0.3395,0.3866 and 0.4494,respectively,reflecting obvious regional differences in the lake ecosystem health.The current study may provide useful information for wetland restoration and management.