Objective：To analyze the clinical efficacy of minimally invasive occlusion via thorax in the treatment of atrial septal defect （ASD）. Methods：Clinical data of 63 patients with ASD were analyzed. The age of the patients was （32.47±17.66） years old and the maximum diameter of ASD was （26.22±9.75） mm. Heart function grading according to New York Heart Association（NYHA）：23 patients in class Ⅰ， 32 patients in classⅡ， 8 patients in class Ⅲ. There were 9 patients with severe pulmonary hypertention. All pa－tients were under general anaesthesia and a small incision was made in the 4th intercostal of the right sternum. The occluder was re－leased using monotubed unit，with the help of normal transchest echocardiography. Results：The procedure was successfully completed in 61 patients.The diameter of the occluder was （33.88±10.51） mm，（7.97±2.27） mm larger than the maximum diameter of ASD. The patients were discharged at （6.09±2.58） d postoperatively. No atrial shut or embolism was found within 3-51 months after the operation.The heart function was improved in all patients. One patient was converted to surgery under cardiopulmonary bypass and one patient discontinued the operation due to the failure in the occlusion. Conclusion：ASD occlusion via thorax is minimally invasive and safe.