The application of machine vision technology on Epinephelus malabaricus’  abnormal behavior identification and alarm in time is helpful to improve the Epinephelus malabaricus’ survival rate, reduce the loss of human resource in the breeding process. Under the condition of constant ammonia nitrogen, temperature, Ph value, through artificial adjusted water dissolved oxygen concentration in order to get Epinephelus malabaricus’ images under normal and abnormal conditions, using foreground extraction, binarization, open operation, median filtering method to process collected images , then two images undered normal condition and abnormal condition were selected for differential operation to get the differential Image. Using the fisheye shape to get the fisheye center coordinates, Cuting out the image contained only the  fish mouth by the  fisheye center coordinates. According to the fish mouth area to judge the fish mouth is closed or opened and how long is the fish mouth closed or opened, If the fish mouth is opening sustained for 2 minutes, as the fish appeared abnormal behavior and alarm. Using 50 Epinephelus malabaricus of equal size to verify this method, indicated that the method can effectively identify the abnormal behavior of Epinephelus malabaricus. The proposed method is beneficial to improve the efficiency of the aquaculture, promote the development of modernization of aquaculture.