Abstract: An intrusion detection system and intrusion detection method are provided. The intrusion detection system includes multiple IoT devices and a central control device. The central control device is configured to obtain multiple sensing pairs from a paired combination of the multiple IoT devices; create a sensing-pair list including the multiple sensing pairs and features of each sensing pair; obtain multiple first pairs whose features satisfy a first feature condition from the sensing-pair list; dynamically schedule the multiple IoT devices to send and receive signals in a time sharing fashion to obtain a first sensing signal of each first pair; and based on a paired node of the multiple first pairs, count a first status code and a second status code of the multiple first pairs to which each paired node belongs, to determine whether any intrusion condition occurs.