Abstract: Traditional target hovering detection methods have many limits and shortages which cannot accurately determine the target behavior.In this paper,object trajectories are gridded,a new target detection method for moving object trajectories was proposed.Firstly,the moving targets were detected with the background difference method.Secondly,the moving target in image sequence was tracked according to the Camshift algorithm.Then the moving target trajectory in the defense area was gridded and some statistics were analyzed.At last,the hovering behavior was detected and the alarm was triggered.The experiment results show that this method can judge several typical hovering behavior accurately and in real-time.