Ecosystem service is a very important issue for current, sustainable scientific research. Environmental protection and management requirements are increasing and policymakers hope to incorporate ecological service information into decision-making and consultations. Because of theory uncertainty and methods limitation, it is, at present, very difficult to accurately evaluate ecosystem services and extract important ecosystem services information that can help decision-makers meet the demands of various stakeholders. In this study, we first identified and defined ecosystem service potential supply, actual supply (flow), and human demand based on the processes and mechanisms involved in ecosystem service generation and delivery. Two indicators were then introduced, the supply rate and supply-demand ratio, which provide a mean that can be used to compare the status of natural capital between regions. We also investigated the ecosystem service matrix and GIS spatial simulation technology and used these indicators to investigate the Baiyangdian River Basin as a case study. The aim was to reveal the spatio-temporal characteristics of service supply and demand. The supply rate and supply-demand ratio for the Baiyangdian River Basin in 2010 were 0.4966 and 0.1131, respectively. This indicated that the ecosystem service supply status was good and in surplus. The places with high supply rate should be considered as hotspots for ecological protection and compensation. However, places with high ecosystem service demand should concentrate on ecological construction and restoration. The results provide a scientific basis for regional ecological environment management and policy-making.