From a global perspective, the ecological sustainability of building systems has always been a hot research topic, especially in China, where the annual amount of new construction is nearly half of the world. The difficulty is making a complete and accurate ecological assessment of the building system. This study has designed and adopted the LCA-Emergy-ANN framework to assess and analyze an airport building system for sustainability. The results demonstrate that building material emergy and operational stage emergy play a critical role and account for 92.4% of the entire emergy, which are the primary contributors. As the vital indicator, the emergy sustainability index (ESI) is 0.669, which is unsustainable (The eligibility standard is 1). Simultaneously, to ensure the accuracy of the data results, sensitivity analysis was performed. The artificial neural network (ANN) was used by integrating the LCA method and emergy approach to predict the sustainability trend in the long run. In the end, the optimization strategy is proposed to enhance the sustainability of the building system.