The invention discloses a transboundary intrusion detection method for a security sensitive area, and belongs to the field of video security monitoring. The method comprises the steps of 1) acquiring,by a camera, images in real time and setting an acquisition area of the camera as a security sensitive area; 2) extracting moving object information from an acquired video stream by using a background subtraction method; 3) processing an extracted foreground image by using a morphology filtering method, that is, moving objects; 4) extracting outlines of connected areas in the foreground image, screening the moving objects and removing the connected areas with undesirable areas, sizes or proportions; and 5) determining whether the moving objects enter a preset security sensitive area by usinga vector cross product method. The method of the invention can effectively screen out transboundary invasion events in a monitoring area, reduce the work load of monitoring personnel and avoid the omission of reports of abnormal events caused by the working fatigue of the monitoring personnel.