The invention provides a method for video monitoring and prewarning of the intrusive external force, comprising the following steps of carrying out background modeling on a warning region; carrying out modeling on the external force which can intrude; carrying out real-time video collection on the intrusive external force which enters the warning region, carrying out foreground detection, and extracting foreground information from a background of the warning region; comparing the extracted foreground information and characteristic information in modeling to judge whether the intrusive external force needing monitoring exists or not; if the intrusive external force needs monitoring, carrying out target location and/or motion state tracking on the intrusive external force; when a result of target location and/or motion state tracking on the intrusive external force achieves a warning level, starting a field warning device to warn, and/or sending prewarning to a remote monitor end, and also sending video information which is collected in real time to the remote monitor end. The invention can carrying out video monitoring and prewarning on the intrusive external force of the warning region of a transmission line, thereby reducing or eliminating the condition that the external force destroys the line.