Abstract: AIM: To explore the feasibility of establishing animal models with equal-sized atrial septal defect(ASD) in canines using the puncture method without cardiopulmonary bypass.METHODS: Nine healthy mongrel canines were chosen for the study.Atrial septum was palpated through the epicardium of the right atrium after thoracotomy to determine the position of the oval fossa followed by the insertion of 6-mm homemade atrial septal perforators that were then pushed vertically to puncture the atrial septum.Atrial septum was cut annularly and ASD models were thus established.RESULTS: Operations were successful in all nine dogs.Postoperative anatomy of two of the dogs showed that the ASD diameters in the two dogs were 6.0 mm and 6.1 mm,respectively,the size of the homemade punctures.TTE displayed that the ASD diameters in the other seven dogs were(6.0±0.2) mm and all were central-type ASD.No complications such as pericardial effusion were observed in the nine dogs.CONCLUSION: Puncture of the atrial septum is effective and safe in establishing equal-sized ASD animal models without cardiopulmonary bypass.