The ability of animals to respond to different life-threatening stimuli and take the most adaptive defensive behavior is essential for survival and breeding. Studies have found that a gradually expanding black disk in the upper field which simulates the looming of natural predators approaching from above can induce different instinct defensive behaviors of mice, including freezing or flight. In conventional animal behavior studies, time and labor-consuming manual operations are used to generate the stimuli, limiting the efficiency of animal behavior studies. In this paper, we have developed a closed-loop animal behavior regulation and analysis system. Based on this system, we have studied the defensive behavior of mice facing different stimuli. Looming with low gray value or low-frequency light stimulation would induce the freezing behavior of mice, which tend to escape to a safe area under looming with high gray value or high-frequency light stimulation. This study has demonstrated an automatic behavior regulation system capable of delivering random stimuli, which can further improve the efficiency and accuracy of the experiment.