The invention discloses a real-time intelligent monitoring method based on natural video. The method uses the knowledge of computer image processing and artificial intelligence and realizes unmanned intelligent monitoring and alarm to the action of pedestrian in public places and important sensitive places. Firstly, video frame serial sections which need to be studied are extracted, movable historical images are obtained, which reflect the movement process of the people; on this base, the user-defined method for extracting the eigenvector is used, vector representation of the specific movement series is obtained, and the vector sample is stored in the sample database; as for the video frame serial which need to be monitored, the eigenvector and sample data are mapped in the low dimensional space, the corresponding classification by the optimized method is obtained and alarm is carried out. Owing to the sample study mechanism and the classification mechanism of the designed actions in the text, the method of the invention improves the accuracy of identification and strengthens the expansibility of identification; by designing the eigenvector representation and extraction method of movement serial of the people, the completeness and accuracy of action representation are strengthened.