Many cities are facing environmental challenges with rapid urbanisation and industrialisation. It is critical to evaluate this new urban reality and its sustainability potential to generate appropriate solutions for a sustainable future. The urban metabolism framework is commonly applied to understand appropriate strategies to achieve sustainability for urban systems. In this study, material flow analysis was applied in conjunction with specific socio-economic indicators to model urban metabolism and evaluate appropriate urban metabolism changes for Jinchang City, China between 1995 and 2014. Structural decomposition analysis and decoupling analysis were used to explain and evaluate the sustainability potential of Jinchang City. Changes in material consumption and the waste generation of Jinchang City indicated a long-term unsustainable trajectory, evidenced by continuously increasing material inputs and outputs. We also found a significant reduction in air pollution, with declining sulphur dioxide emissions and dust; all are indicators of improvement in air quality. What is of special note is that industrial production was concurrently greatly increasing. These indicators suggest a positive improvement in sustainability beyond simple incrementalism. The study showed that MFA techniques can be used as valuable tools for understanding urban metabolism, evaluating urban sustainability, and suggesting strategies for the timely addressing of urban sustainability issues. This strategy is important in the face of China’s increasing industrial capacity.