Embodiments of the present application provide a regional surveillance and alarming system and an alarming method. In the embodiment of the present application, each security region is provided with a control device having stored thereon an association table in which associated objects of a security region where the control device is located when this security region is taken as the first target object are recorded, and the associated objects may be a detection device or other target objects. When a change of the state of the detection device or the target object satisfies the alarm output triggering condition, the control device may issue an alarm. As such, a real-time surveillance and alarming of illegal events may be allowed.