A review of disaster prevention and mitigation practices in China and abroad reveals that resilience-based approaches, which prioritize post-disaster recovery capabilities, have inherent limitations in guiding China’s urban disaster prevention and control. Therefore, it is urgent to build a new theoretical framework that can integrate all four stages of disaster response: prevention, response, recovery, and learning, thereby maintaining essential urban functions under extreme events that exceed a city’s designed defense capacity. Drawing inspiration from human immunology, this study proposes a theory of disaster-immune cities. In this framework, cities are conceptualized as living organisms with disaster resistance and immune defense mechanisms categorized into three levels: innate, adaptive, and memory. The inherent immune mechanism should serve as the core objective of urban resilience construction. This mechanism ensures that key urban operational functions—representing the fundamental vital signs of the city as living organisms—are maintained at an acceptable level when confronted with various "viruses” of historical memory intrusions. The memory immune defense mechanism dynamically operates throughout the entire disaster response process and manifests in subsequent disaster cycles, reflecting the system’s accumulated experience, adaptation, and learning outcomes. The key distinction between the theory of urban disaster immunity and the resilience theory is its explicit framework for robustness analysis, which ensures the maintenance of critical urban functions at acceptable levels, along with its emphasis on system optimization and coordination among subsystems. Compared with risk-based theory, the immunity-based approach shifts the focus from probabilistic risk control of critical urban functions to defining and safeguarding threshold levels for the essential operational functions of the system.