Objective To optimize the preparation of air bag materials for abdominal withdrawal reflex test .Methods By digital vernier caliper and X ray imaging measureme of the diameters of different air bags in different pressure values. Using the pain threshold(3 points) as a criterion to test the pressure values of different air bags in the rats with visceral pain sensitivity. Results With the pressure increasing, the diameter change of round latex balloon is uniform and gentle, and can meet the pressure range used in the experiment (20-80mmHg). Threshold of visceral pain in rats near the nociceptive stimulus value，and will not cause irreversible damage to the intestinal tract of rats. Conclusion In the abdominal withdrawal reflex test, round latex balloon for air bag is an ideal material.