Book excerpt: Since the middle of the last century, rapid population growth and urbanization have led to the encroachment of a large number of natural spaces, resulting in a series of ecological security issues such as environmental pollution, resource depletion and habitat destruction, which have severely challenged global sustainable development. Urban ecological security is an important barrier to urban residents' production and life, the foundation and core of national or regional ecological security, and it is of great significance to promote green development and harmonious coexistence between humans and nature. With global warming, frequent natural disasters and other multifactorial threats, the issue of ecological security in cities as centers of the settlement have become a focus of international attention. However, cities are complex systems with social, economic and natural conditions coupled with each other. Under the overlapping of many factors, the basic problems such as the mechanism of urban development on ecological security have not been fully explained, and there is also a lack of quantitative assessment methods corresponding to urban ecological conditions, let alone simulation and prediction.