The invention relates to an intelligent monitoring method, device and system based on WiFi. The device comprises an intelligent WiFi AP (Access Point), which is used for detecting a WiFi signal intensity value in an early warning area, judging whether the WiFi signal intensity value is within a preset signal intensity range, judging whether the current early warning count exceeds an early warning count threshold after a set timing cycle, if so, sending and displaying prompt information, otherwise, not carrying out any processing. The method, the device and the system realize intelligent monitoring using the WiFi technology, thereby effectively avoiding user privacy divulgence and missing report defect; and intelligent monitoring can be realized by adding only one WiFi connector and sufficiently utilizing the existing household routing platform, so the method, the device and the system are low in cost, high in security and very suitable for large-area popularization.