This study analyzes and evaluates the status and long-term trend of regional economic sustainability in eastern Anhui Province, China. Based on the triangle model and the definition of economic sustainable development, this study evaluates the interrelationship among regional economic development, resource-energy consumption, environmental pollution, and ecological performance. The sustainable and comprehensive utilization situation in the study region from 1975–2012 is examined. The results show that in 2012, the comprehensive development in the study region had a general status in terms of sustainability. The sustainable development trend of the seven administrative subunits inside the region had a weak and general status in terms of sustainability, while the status of sustainability in the southeastern part of the region was better than that in the northwest. During the period from 1975–1998, the study region’s comprehensive development presented a trend of general sustainability. In the period from 1998–2012, the region experienced a trend of very strong sustainability in its development. These statuses and trends have a certain relationship with the study region’s strong economic development and environmental protection over the past 37 years. The triangle method, as an intuitive platform for illustrating sustainability status and trends in economic development, seems to hold promise as an analytical management tool given its simplicity, ease of use, and flexibility.