Abstract: A non-intrusive load monitoring system, including a device classification and prediction sub-process, a new device identification sub-process, and a classifier self-training sub-process. By means of the configuration of these processes, the defect in accuracy of identification of a new device in the prior art is overcome; and when a device other than the devices in a device database is detected, data of the device can be intercepted and stored in the device database, so that the function of accurately identifying existing devices in a device database can be achieved, and the device database can be automatically updated when a new device other than the devices in the device database is discovered.