Climate change and urbanization have a profound impact on the safety and sustainable development of coastal cities in our country. " Climate adaptation" has become a strategic consensus of cities on climate change. In this paper,based on the theory of complex adaptive systems (CAS) ,this paper constructs a theoretical framework for the climate adaptation and optimization of coastal urban spatial structure. It analyzes the complex adaptive features of " spatial structure" and " climate change" and discusses the interactivity of adaptable subjects of urban spatial and climate systems,Complexity and adaptive process mechanism to build a climate adaptation model of urban spatial structure,and carry out empirical research with Xiamen as a specific case city,in order to provide a scientific basis and technical support for the coastal city of China to address climate change and adapt to climate change planning.