Objective To optimize the preparation of air bag materials for abdominal withdrawal reflex test. Methods To measure the diameters of different pressue-air bags by digital vernier caliper and X ray imaging. Using the pain threshold (3 points) as a criterion to test the pressure values of different air bags in the rats with corresponding visceral pain sensitivity. Results With the increasing pressure, the changes of the diameter of round latex balloon were uniform and gentle, and could meet the pressure range used in the experiment (20~80 mmHg). The threshold of visceral pain in rats was near the nociceptive stimulus value,and would not cause irreversible damage to the rat intestinal tract. Conclusions Air bag made from round latrex ballon is an ideal tool to be used in abdominal withdrawal reflex test in rats.