Objective To investigate the effect of body weight on the induction of mild hypothermia in a rabbit model of asphyxia cardiac arrest. Methods Twenty-four rabbits were randomized into two groups: the ice bag group and the intravenous 4℃ saline group. Cardiac arrest was induced and after 3 minutes of cardiac arrest, cardiopulmonary resuscitation was begun. Simultaneously, mild hypothermia was induced by putting an ice bag over the abdomen or infusion of 4℃ saline via an ear vein. A 2℃ decrease of rectal temperature was considered as the completion of hypothermia induction. Induction times were recorded, compared, and analyzed with respect to body weight. Results All rabbits had restoration of spontaneous circulation (ROSC) and ROSC lasted during the experiment. Induction time in the ice bag group was significantly shorter than that in the intravenous 4℃ saline group (22.8±4.7 min VS 42.5±4.0 min, P< 0.001). Induction time significantly correlated with body weight in the ice bag group (Pearson Correlation: r = 0.725, P = 0.029), but not in the intravenous 4℃ saline group (Pearson Correlation: P = 0.418). Conclusions In a rabbit model, induction of mild hypothermia with an ice bag is faster than with intravenous 4℃ saline; induction time positively correlates with body weight when an ice bag is used, but not when intravenous 4℃ saline used. The effect of body weight should be considered when choosing an appropriate method to achieve early induction of mild hypothermia.