The invention belongs to a detection method based on a group environment abnormal behavior in the technical field of computer motion image identification and monitoring, comprising the following steps of: dividing video unit subsequences in the establishment of a detection model, extracting characteristics, establishing a sample database and establishing an Multi-HMM model; extracting the sequence of each observed value from a video sequence of the current monitoring scene in abnormal behavior detection, confirming the optimal hidden Markov chains corresponding to the sequences of the observed values, and judging and warming abnormal behaviors. By accurately and rapidly extracting the dynamic changing characteristic of a video sequence on the frequency domain along with the change of timebased on the whole angle and automatically detecting abnormal behaviors under group environments in real time according to the established model, the invention achieves the accuracy rate of about 90 percent, thereby having the characteristics of accurately and rapidly extracting the behavior characteristic of the current monitored scene, being widely used for detecting the abnormal behaviors happened under the group environments, having high detection efficiency, accuracy and reliability, and the like.