Territorial spatial planning involves fixability and flexibility in different driving factors related to control and development orientation, and they play an important role in regional sustainable development, especially in developing countries such as China. With rapid urbanisation and industrialisation, China has been impacted by conflicts between development and protection in territorial space. To integrate the contradictions among different territorial spatial planning measures, planners and scholars have started to focus on studies regarding fixability–flexibility relationships and integration. However, the relationship between and integration of fixability and flexibility in territorial spatial planning have yet to be clearly summarised. This paper explores an innovative research direction for the fixability–flexibility relations in territorial spatial planning from a new perspective, the Food–Energy–Water Nexus, which is a dynamic and comprehensive framework for Sustainable Development Goals (SDGs) studies. This paper covers the existing research on fixability and flexibility in territorial spatial planning. Moreover, after summarising the conflicts of fixability and flexibility, the dialectical relationship between and the integration of fixability and flexibility are researched.