Abstract: Objective: To make a model of sever hypothermia using cold seawater and obsever trend of cardiac function and serum lactic acid Methods: Each dog was immersed in cold seawater Results: When the retum temperature of dogs reached （25±0 5)℃,its cardiac output,heart rate decreased and PR interval increased,and serum lactic acid increased. Conclusion: cardiac function of hypothermic dogs decreased and serum lactic acid increased